141

Physics, Astronomy & Cosmology / Re: Is time dilation present inside of a hollow sphere?

« on: 25/04/2017 03:21:56 »

No net gravitational force inside the hollow shell doesn't mean that there isn't a difference in gravitational potential between being inside the shell vs. outside the shell.( think of this way: you would have to do work against gravity to move from inside to outside of the shell). Since gravitational time dilation is related to difference in potential,  a clock inside the shell would run slower than on on the surface even though the one on the surface feels a non-zero g force and the one inside feels none. 

142

New Theories / Re: Are there flaws in the theory of special relativity?

« on: 24/04/2017 20:44:30 »

Dear  Janus and Goc,

Your SR calculation is correct. I want to repeat for other viewers of this topic:

The ship’s speed is 60 % c and it travels toward + x. Two photons (toward +x and –x) is emitted at the moment To = 0  worldsec.

We seek the coordinates of these photons according to the ship at the moment Tı =10 worldsec.

]The results  acoording to the world:

(x’ ;  t’) world  ===> (3 000 000 worldkm; 10worldsec)

(x’’ ;  t’’) world ===> (-3 000 000worldkm; 10 worldsec)

The results according to the ship:

(x’ ; t’) ship  ===>   (1 500 000 shipkm ; 5 shipsec)

(x’’ ; t’’) ship  ===>  ( 6 000 000shipkm ; 20 shipsec)

I have never/any objection for these results. And nobody objects these result in accordance with SR mentality.

BUT; probably, you may distinguish a contradiction too:

How does the clock (in the ship) indicate either 5 shipsec or 20 shipsec simultaneously?

How does the  shipclock or abstract time of the ship work by two (innumerable  for angled positions) different tempos?

Is there time contraction in SR (20 shipsec represents time contraction instead of time dilation)

 The time moment is unique;  10 worldsec, 5 shipsec and  20 shipsec represent the same moment in accordance with the existence of photons.

The answer to your question of how S's clock can read 5 and 20 sec simultaneously is that it doesn't.


To illustrate, lets modify this set up slightly.  The A and S frame have measuring rods extending outward in each direction to a distance of 3,000,000 km as measured by their own frame. At the ends of these rods are clocks which are synchronized according to each frame (as far as the ship is concerned the clocks at the end of its rods read the same as the ship clock and as far as A is concerned the clocks at B and `B read the same as his clock.  The following set of images show events as far as A measures at three different times for A, 0 sec, 5 sec and 10 sec.
Since S and its rods are moving at 0.6c relative to A and its rods, the rods are length contracted and none of the clocks moving with S are in sync with each other, due to the relativity of simultaneity.

The top image is the start of the scenario.
The middle image is after 5 sec has passed for A B and B'. The light pulses are halfway to to B' and B, and the left going pulse has just reached the end of the left rod of S. Since all these clocks are time dilated, the Clock at this end has advanced 4 sec to now read 10 sec. This is just as it should be, as according to S, the light should also reach this end when the clock there reads 10 sec.  Also note that when the clock at A reads 5 sec, it is bit more than 7.5 marks on S's measuring stick from S.(this will be touched on again later).
The bottom image is when the time for A is 10 sec. The light has reached both B' and B, and the clocks at those points read 10 sec. The three clocks moving with S have all advanced 8 sec due to time dilation. Again note where A is relative to S's measuring stick. Also note that B is ten of S's measuring stick marks from S.

Now we'll look at the same events according to S. Here we will show 5 different points of time:
The starting point,
When the light reaches B
When A's clock reads 5 sec
When A's clock reads 10 sec
When the light reaches `B



Top image. Now it is A and its clocks and rods that have the relative motion(to the left), so they undergo length contraction and the clocks are offset from each other due to the relativity of simultaneity.
Next we have the light reaching B, this occurs when S and its clocks read 5 sec.  The Clock at B having started at 6 sec and advancing 4 sec reads 10 sec, just like it did for the last set of images. It is also ten mark away from S by S's measuring stick, which also agrees with above.
The other light pulse has yet to reach B'
Next is when A's clock reads 5 sec. The right light has passed B, but the left light has still not yet reached `B. Note when A's clock reads 5 it is next to the same point of S's measuring stick as it was in the last set of images.
Now we show when A's clock reads 10 sec. Again note that A is next to the same point of S's measuring stick as in the last set of images.
Lastly we show when the light finally reaches `B and the clock at `B reads 10 sec. At this point S's clock reads 20 sec.
So according to S, its clocks read 5 sec when the light reaches B and 20 sec when the light reaches `B.  But just because these two events are simultaneous according to A does not mean that A reads 5 sec and 20 sec simultaneously. (in fact, according to A, when the light reaches B and `B, the clock at S reads 8 sec.)  It just means that these events are simultaneous in one frame but not in the other. This is the whole gist of the relativity of simultaneity, that simultaneity is not absolute, but is frame dependent.  The fact that A measures these events as simultaneous has now priority over the fact that S measures them not to be.  S in turn measures the fact that the light reaches the end of its measuring rods simultaneously, while A says its does not.  Neither frame is more correct than the other.
Neither does this create a contradiction. Because both A and S will agree what happens when any two points of their frames pass each other.  If I were to put clocks at each of the tick marks on both sets of measuring rods, whenever two of those clocks passed each other both A and S would agree as to their respective clock readings.

So no, you have shown a contradiction in SR. (And let's be honest, if Relativity could be proven wrong by such a simple example, it would been dumped decades ago.  Scientists don't make a name for themselves by just going along with the flow, they do it by overturning the boat, and someone would have jumped on this chance long ago.)
 

143

Physics, Astronomy & Cosmology / Re: Are black hole mergers impossible?

« on: 17/12/2016 20:35:06 »

Since time slows down at the event horizon of each black hole shouldn't it take an infinite amount of time for the process to conclude?

Imagine you have two 100 solar masses black holes, they will have event horizons radii of 295 km.  When their centers are 590 km apart, their event horizons touch. Keep in mind that the event horizon is not a physical thing, but a boundary.   But, the event horizon radius is directly proportional to the mass and the total mass of the two BH's is 200 solar masses and the thus event horizon of the new black hole will be 590 km, or equal to the distance the centers are now apart.   In other words, the event horizon for the combined mass of the original two black hole expands to include the singularities of both black holes before the singularities get as close as the original event horizon radii.

Here's a diagram showing a pair of black holes merging. the circles are the extent of the event horizons.

144

Physics, Astronomy & Cosmology / Re: How many photos are emitted by the sun every second? How many reach earth?

« on: 14/12/2016 00:13:42 »

If we use the 1e45 figure for photons/sec emitted by the Sun, then you get ~1.8e36 photons striking the Earth per sec and 4.4e16 photons per sec hitting the eye (assuming a pupil diameter of 2mm.)

However, the eye figure doesn't take attenuation by the Earth's atmosphere, accounting for that leaves us with ~3.4e16 photons per sec hitting the eye.  This works out to 0.013 watts entering your eye if you are staring directly into the Sun (Not a good idea.)

Using the second, smaller figure would decrease the photon count by a factor of 2000 in each case (but not the wattage)

145

Plant Sciences, Zoology & Evolution / Re: Is evolution even science, or just gross intellectual dishonesty?

« on: 12/12/2016 17:50:19 »

Random acts, even if they might result in any benefits, will always result in far more chaos. For example, even if you believed that if you threw a pile of bricks off a roof billions of times they would eventually fall into a perfectly constructed house with walls, closets and an attached garage, a vast majority of the time, though, they would unquestionably fall into meaningless configurations.

Genes, chromosomes etc. are not bricks.  They don't just take on any random configuration and can only combine in certain ways.  They also are more analogous to the blueprints of the house rather than the building materials.  Mutations are small alterations to those blueprints.   Of course, you might instead be referring instead to the original formation of life, abiogenesis instead here.  But even abiogenesis is not just a random throwing together of chemicals, as those chemical themselves have rules that govern how they can join up.  Besides, abiogenesis and evolution are two completely different things and are not related to each other, even though some people try to lump them together into a single argument. (now that's intellectual dishonesty) 

The same is true with genetics. Randomly rearranging genetic material generally result in grossly deformed and diseased organisms. For every fossil of a viable-looking organisms we should have found billions of fossils of diseased and deformed organisms. They're not there. The vast majority of fossils show well-formed, functional-looking creatures. The fossil record proves beyond any question that evolution never happened.

Mutations are not the random remixing of genetic material. they are small changes to one part of the blueprint.  Some mutations are benign (the Siamese breed of cat is a result of a mutation that altered its pigmentation.),  Some will be harmful, and some will turn out to be beneficial. (if not immediately then at some later point.  If the mutation is harmful or produces a malformed individual, that individual will either not survive or won't reproduce, and the mutation never gets into the gene pool. (If it hadn't been for the fact that people found the unique pigmentation of the Siamese cat desirable, they would have bred it out instead of for it and you wouldn't see that breed of cat today)   Mutations effect individuals, while evolution effects populations.   Only those mutations that do not hinder the individuals reproduction will be passed on to later generations and spread out into the population as a whole. 
The mutation rate also is fairly low in any given population. (if it goes too high, you risk not producing enough viable offspring to maintain the population.) As a result, the number of undesirable mutations resulting is malformed individuals is going to be vert low compared to the population at large (And the majority of these won't survive infancy).  The fossil record is sparse when compared to the number of creatures that have lived in the past.  The conditions which produces a fossil happens rarely and the vat majority of the time a deceased animal leaves no lasting record.  Pure common sense tells us that if if the fossil record is only represents a tiny fraction of past animal life and that malformed individuals would only be expected to be a small fraction of that, that you would not expect to find "billions" of fossils of malformed individuals. To suggest otherwise is again to be intellectually dishonest.

Then, to say that evolution was not random, as some have suggested, yet still call it evolution, is as ludicrous as calling a bird a giraffe -- if it flies it's not a giraffe.

Evolution is the combination of small random mutations to the individual coupled with natural selection on the population level. Those mutations that do not hinder the individual's reproduction, are passed on, those that do, are not.  That's evolution; the slow alteration of a population over many generations.

The bottom line is the fossil records shows that new species make their first appearance as functional creatures, not as a result of survival of the fittest. Where are the myriads of "unfit" that should have existed? Such a sudden appearance of new, viable life forms, which is confirmed over and over by the fossil record, rather than support evolution, thoroughly disprove it.

"Unfit" is a relative term.  A creature that is unfit under one circumstance, is the fittest under another.    Let's take the  giraffe for example.  You start with an animal that grazes on low shrubs.  In a population you are going to have a certain genetic variation in terms of neck length. This will vary over a certain range, with necks too long or too short selected against.  But now the climate begins to slowly change and the low shrubbery is going away in favor of trees. Those animals with longer necks find themselves having a slight advantage over those with shorter necks. The shorter necked individuals can't compete as well, produce fewer and fewer offspring and this trait is selected against. A new "norm" has been established for neck length.  This also means that mutations that produce even a longer neck will be selected for, when earlier, it would have been selected against (the too long neck being more of a hindrance for a low level browser.)   So a really long neck is "unfit" under certain conditions, but more fit under others.  "unfit" doesn't equate to non-viable, but just not a good fit for the circumstances.  "Survival of the fittest", just means that those individuals that have a genetic trait that gives them a competitive edge, is going to be more successful, and be more likely to produce offspring and pass that trait onto later generations. 

All your arguments themselves have been a type of intellectual dishonesty known as the "strawman fallacy".   You have erected a "strawman" version of evolution and knocked it down rather than actually arguing against the theory itself. This is why people keep telling you that you need to learn about evolution and what it actually says. Otherwise you are arguing against some imaginary version of it that is of your own making. (And ending up looking foolish in the process.)

146

Chemistry / Re: Why doesn't water burn?

« on: 06/12/2016 19:17:42 »

Sorry, I work at sea, and there is a chance that if our boilers are leaking and emitting too much water vapour through the stack that we have fires caused by this water, which we call hydrogen fires. which as you point out is NOT the same as hydrogen flame.

Okay, After a little research, I found out what is happening with your "hydrogen fire".  Under really high temperatures (+1000C) the water vapor in the stack will chemically combine with the soot in the stack forming H2 and CO which are both inflammable.

147

Physiology & Medicine / Re: Why and when does your voice get old?

« on: 22/11/2016 20:36:11 »

The vocal chords and the muscles controlling them age just like the rest of your body does.  Just like you can't be as athletic when you reach a certain age as you were when you were younger, Your vocal chords can't respond as well.  In addition, most people suffer some hearing loss as they age, and since a part of how we modulate our speech deals with feedback we get from what we hear, this also has an effect on the final sound of our voice.

148

General Science / Re: Hitting a pendulum

« on: 17/11/2016 22:20:09 »

The kinetic energy = potential energy.  So the answer is actually 4,9j?

Yep.  And so what does that tell you about how fast the mass would be moving at the bottom of its swing if it were released from 90 degree angle?  And what does that tell you about how fast it would have to be moving after you hit it with a hammer at the bottom of the arc to get it to swing up to the 90 degree angle?

149

Physics, Astronomy & Cosmology / Re: Can we detect solar systems with Gravitational waves

« on: 17/11/2016 22:14:55 »

Let's put it this way; The Earth, in orbiting the Sun emits gravitational radiation at a grand total power of just 200 watts. And that it at the source.  The gravitational radiation detected recently had a peak power output equal to 50 times the radiant output of the entire observable universe.

Also consider this, Ganymede, while orbiting Jupiter emits gravitational radiation at 5.6 watts and is much much much closer than the nearest star system.  In other words, gravitational waves just from sources in the solar system would swamp out anything we could sense from another star.

In addition, the gravitational waves from a Earth-like planet orbiting a Sun-like star would have a frequency of 1 cycle per year and a wavelength of 1 light year.

150

Physics, Astronomy & Cosmology / Re: How does the moon impact the tides?

« on: 17/11/2016 19:33:10 »

Tom Ettinger asked the Naked Scientists:
   My question is about the super moon. On the national public radio station in United States there was a discussion of the super moon. In this discussion they stated that the biggest tides were during the full moon.  I can understand why tides are stronger when the effects of the sun and moon influence each other. Why would tides be higher when the moon and sun are opposite in the full moon, rather than to acting together When there is a new moon?
What do you think?

The thing to remember is that the Moon and Sun both produce two tidal bulges each on opposite sides of the Earth.  The tidal bulges are caused by the difference in gravitational force caused by each body across the diameter of the Earth.  If we consider the Moon, Because gravity falls off by the square of the distance, the near side of the Earth feels a stronger pull from the Moon than the center of the Earth does and the far side less pull than the center. In addition, the gravity from the Moon acting on the limbs of the Earth has a slight inward component that squeezes inward.  So just like when you squeeze the middle of a rubber ball the ends tend to bulge out, you get an additional lift to the tidal bulges.   

Now because the Moon is much closer to the Earth, the Earth's diameter is a lot larger fraction of the total distance between them than is the case for the Sun. So even though the net gravitational force of the Sun on the Earth is greater than that of the Moon, the difference in gravitational force across the Earth(or tidal force) is larger for the Moon than for the Sun and the Moon creates the bigger bulges.

151

That CAN'T be true! / Re: How can time be a dimension?

« on: 15/11/2016 17:19:24 »

The idea that time is a dimension has always struck me as suspect. If I go fast enough my length dimension will change according to an outside observer, as will my time--One year passes for me, while 100 passes for him. However, when I return home and stop, my length, according to the same outside observer, will be restored, while my time will not. That is, according to the observer our clocks will again tick at the same rate, but the alteration in my time, because of my trip, will not be restored--I will still be about 100 years younger than him.

However the distance traveled, as measured by you, will be 100 times shorter than the distance measured by you. Your "odometer" at the end of the trip would register a smaller distance, which is the length equivalent of the difference in elapsed time.  In other words, the fact that he sees you length contracted and your tick rate as running slow are like effects and only hold while you are in motion with respect to him.  Your accumulated age and odometer reading at the end of the trip are the hold-overs.  So to say that there is no hold over effect from length contraction is wrong.

152

Physics, Astronomy & Cosmology / Re: If a hole were drilled through Earth and you jumped through, how would you exit?

« on: 13/11/2016 01:48:28 »

You would have to time your exit at the antipodes carefully or you might well start another trip down if you wanted to see what it is like in the middle you would have to look quick as you would be moving at 11.6Km/h

Assuming a uniform density for the Earth, the answer comes out to 7.9 km/sec at the center.    Some of you might recognize that value as it turns out to be equal to the orbital velocity at the Surface of the Earth.   It also turn out that it would take an object dropped into the hole ~84.48 mins to complete a round trip back to where you dropped it. This also equal to the period of a orbit at the Earth's surface.   In other words, if you cleared all obstacles( including the air) from its path an object put in orbit just at the Earth surface, would meet up with your dropped object on the other side and then again back where they started.   When the object reaches the center of the Earth, the orbiting object will have completed 1/4 of an orbit and for that moment they will have the same velocity.

In fact, if you imagine an imaginary line at a right angle to the hole that follows the dropped object, it will intersect with the orbiting object at all times. (Assuming they both start at one end of the hole at the same time.)

This give us a way to determine how far the dropped object has fallen at any time after release.
 This will work out to be ~ (1-cos(0.00124t))R 
Where t is the time in seconds, R the radius of the Earth and the cosine is in radians.

153

Physics, Astronomy & Cosmology / Re: If a hole were drilled through Earth and you jumped through, how would you exit?

« on: 03/11/2016 00:56:30 »

Neglecting air resistance (and other impracticalities), you would oscillate back-and-forth between the two sides of the planet with simple harmonic motion. You would accelerate downwards from one surface, reach a velocity maximum in the region of the Earth's centre and then decelerate to a standstill at the opposite surface.

That's theoretically true - if a perfectly symmetrical spherical object, such a ball-bearing of finest precision, were dropped into a hole drilled through the centre of a perfectly symmetrical planet.  The ball-bearing would oscillate endlessly back and forth.

However, the OP posits that "you", ie presumably a human being, jumps into hole drilled through "Earth".
 
Earth and humans aren't perfectly symmetrical.  Humans have more mass in their head than in their feet, and Earth has more land-mass in the Northern Hemisphere than in the Southern.

Wouldn't these asymmetries affect the oscillations, until the OP's human eventually stepped out of the hole, probably at the South Pole end?

The crust is pretty thin compared to the Earth as a whole.  If you average out the oceanic and continental crust thickness, it averages out to ~13.3 km.  It is also less dense (2.2 g/cc) than the Earth as a whole 5.52 g/cc.   In the end it works out that the entire crust amounts to about 1/400 the mass of the entire Earth.   And while the continental crust is quite a bit thicker than the oceanic crust, you also have to remember that it is floating on the mantel, so it extends deeper into the mantel than the oceanic crust does, displacing some of the denser mantel.  If fact, it displaces exactly the same mass of mantel as the mass of the continent crust floating there.   The continental landmass does not add to the total mass in that part of the Earth.   This isn't to say that the mass distribution is totally homogeneous, but the effect of these variations will be extremely small, and likely swamped out by other factors ( the oblateness of the Earth for one.).

154

Cells, Microbes & Viruses / Re: Why does the skin on my fingers wrinkle when I stay in the water too long?

« on: 02/11/2016 22:57:43 »

Its an evolutionary adaptation.  The wrinkling increases your ability to grip objects under wet conditions, thus the body is conditioned to cause those wrinkles under the proper stimulus.  One of the clues that led to this conclusion was that people with nerve damage did not get this wrinkling when their hands were soaked in water.

155

Physics, Astronomy & Cosmology / Re: If one were to in some miraculous way, able to pee standing on the surface of the Moon, what kin

« on: 01/11/2016 18:49:09 »

It works out to ~6 times further and higher.  As far as the shape goes- At the speed you are likely able to pee at, you will be hard pressed to notice a difference between the shape of the curve on the moon vs on the Earth.  There will be a very slight difference however.  Here's why:

Even on the Earth and neglecting air resistance, the arc will not follow a parabola, instead it follows a section of an ellipse. This is because the direction of the force of gravity is not parallel at all points of its path but rather point towards the center of the Earth, in addition, gravity is not constant with height.  A constant and parallel force of gravity along all points of the path is what is required to get a parabolic path. (in most cases, the real deviation from this ideal case is so small, we can't measure the difference.)

The speed and direction upon launch determines the eccentricity of the ellipse.  On the Moon, where the escape velocity is lower, the same launch speed and direction will produce a path that will be slightly less eccentric (closer to that of a circle) than it would on the Earth,  And thus the arc shape will be slightly different.

To put it another way, imagine you could throw an object a 1.68 km/sec parallel to the ground while standing on the Moon.  This is the circular orbital velocity at the surface.  Assuming no obstacles in its way it would follow a circular path around the Moon maintaining a constant distance above the Moon's surface.

If you threw the same object at the same speed on the surface of the Earth where the circular orbital velocity is much higher, the object's path would follow an ellipse which would intersect the Earth's surface some distance from you.   It is obvious that in the two cases, the object follows a differently shaped trajectory.

P.S.  I should mention that the 6 times further answer I gave above assumes that you are going for maximum distance.  If the initial trajectory was parallel to the ground, then the Moon distance would only be 2.5 times further than the Earth distance.

156

Question of the Week / Re: QotW - 16.10.18 - What would happen if I moved to Jupiter for 50 years?

« on: 30/10/2016 20:11:29 »

A couple of points I'd like to add to this thread.

The comparison between clock on Earth and clock on Jupiter so far is a bit incomplete as it only takes into account the difference in the respective Planet's gravitational fields.  In other words, if all else is equal a clock on Jupiter would run some 20 nanoseconds slower per sec than the clock on Earth.  However, all other things are not equal.  Jupiter orbits further from the Sun than the Earth does.  This means that not only is the Earth deeper in the Sun's gravitational field, it has a greater orbital speed.  These two factor both add up to cause a clock sharing an orbit with the Earth around the Sun to run slower than one sharing Jupiter's orbit.

When you factor this in, it turns out that the clock on Jupiter runs only ~7 nanoseconds per sec slower than the Earth clock when you do a clock to clock comparison.

We do this same combination of gravitational time dilation and time dilation due to speed when dealing with satellites orbiting the Earth and comparing their clock rates to ones on the surface of the Earth.   For lower satellites, the speed factor dominates and the satellite clocks run slow, for higher satellites, the position in the field dominates and the clocks run fast. The dividing line is at an altitude which is equal to half the radius of the Earth.
GPS satellites orbit below this altitude, so they run slower than a clock on the surface.

One last point, Someone mentioned that clocks at high altitude run fast because they are in a weaker gravity field. This, I fear, is misleading as people can take this to mean that it is the local strength of gravity that is the factor that determines gravitational time dilation. This is not the case, It is the difference in gravitational potential.

To illustrate the difference, let's use two different planets to compare clocks, Earth and Uranus.   We will use the " all other things being equal" approach and compare clocks just due to the the planets' gravitational fields.
Doing this, we find that that a clock, according to Gravitational time dilation, will run slower on Uranus than it does on the Earth, However, if we compare surface gravity of the two clocks, Earth's surface gravity is the greater of the two.  A clock on the surface of the Earth will feel a greater gravitational force, but the clock on Uranus will run slower by virtue of being in a deeper gravity well.

157

Physics, Astronomy & Cosmology / Re: Why So Many Ambiguous Labels Of Spacey Stuff ?

« on: 23/10/2016 16:06:19 »

Dearest Spacey Bods ,

As a sheepy I of course luff Space, its like well big and makes for a pleasant view on a cloudless night in a light pollution free zone.

Do you not think that some of the labels attributed to spacey stuff is a little ambiguous and need bringing up to date ?

eg :

Big Bang !...it was not a bang innit ?...it was not an explosion which is what most people think innit ?

The term was originally coined by supporters of the steady state model.  It was meant to be denigrating. The proponents of the expanding universe model decided they liked it and adopted it, Much the way the song "Yankee Doodle" was written by the British to make fun of Americans, and the Americans took it on as a song of pride.

Dark Matter....is it really dark and is it really matter ?

Dark as opposed to luminous, yes.  And the present evidence is that it is likely to be particulate in nature, So unless we can definitely rule this out, matter is as good a term as any other.

Dark Energy ....is it really dark and Is it really energy  ?

Making the two above have similar names makes ewe think they related in some way innit ?

We already had dark matter, so when the accelerated expansion of the Universe was discovered, dark energy seemed the natural choice. Once we actually learn more about it, we may change the name. But then again, we might not.  We still use the term cathode ray tube, when it long been known that "cathode rays" are actually electrons, and we never renamed X-rays even though the X originally stood for "unknown".  It may cause some confusion among the general public,  but as long as those in the field know different, I don't think the similarity in names really manners.

Black Hole ......they not completely black and not really holes are they ?

A number of terms have been used over time "collapsar" and "frozen star", are a couple. Black Hole is just the one that stuck. Some times a name is chosen for the way it flows rather than its accuracy of description. The quark was named from a line in "Finnegan's Wake", and the term google for 10^100 was invented by a mathematician's young son.

Nova a star that momentarily brightens up

Supernova a star that brightens up then explodes !

Hypernova badass version of a supernova

The latter two denote an explosion  the original "Nova" term does not

Nova has a long historical significance,  It means "new" and was used to designate any time a new or "guest" star briefly appeared in the sky.  This was long before anyone even knew what the stars actually were, let alone what was causing the new one. In the same way, asteroids got their name because they were just star-like points of light even in telescopes and "aster" means "star".  But long after we know that they are small rocky bodies, the name persists.

With all the modern info that is discovered, do you not think that renaming things would be appropriate to bring them up to date ?



whajafink ?

hugs and shmishes


mwah mwah mwah

Neil
xxxxxxxxxx

Space is big and very diverse
Glad they called it the Universe

"Uni" means "one", and has nothing to do with size or diversity.  "Universe" basically means "the one unified whole".

Maybe there should be some legislature
About changing the spacey nomenclature[/b]
lol

The IAU decides on the nomenclature( they are the ones who recently came up with the new definitions that degraded Pluto from planet to dwarf-planet.) I think it would take quite a bit for them to change some of these names due to their long time usage, and in some cases, the historical significance.

158

Chemistry / Re: Why do we add elements to the periodic table that decay instantly?

« on: 21/10/2016 22:54:40 »

Thanks to evan, janus and chiral for all your valuable comments.

The point that "heavy" elements are always getting created in supernovae, is one that I realised with a head-smack after posting.  But I didn't to bother to edit, as it was obviously bound to get picked up.

However, going back to the original question, about whether very transient, swiftly-decaying elements should be added to the Periodic Table.  I would say not, because it would make the list of "elements" too long.

If I might cite a comparable example from Astronomy.  The list of "planets" in the Solar System was eight, until the year 1930.  In that year, a new "planet", Pluto, was discovered.  Right from the time of its discovery, there were doubts whether "Pluto", should properly be added as a planet, as it's very small.  However it got accepted until 2006, when the IAU threw it out. 

This was because a lot of new objects were being discovered, like Eris, which is bigger than Pluto. So if you accept Pluto as a planet, you'd have to accept Eris too. And there were more objects of comparable size.  You could eventually end up with a list of 40 or 50 "planets".  Which is far too long.

So the IAU demoted Pluto to dwarf status.  Now astronomers (well, most of them), only acknowledge eight planets on the list. Pluto and the rest are regarded as interesting, but not genuine.

Couldn't this approach be adopted with the Periodic list of elements?  That's to say,  physicists and chemists, should only recognise 92 genuine elements, the rest being merely interesting?

Because half-life doesn't make a good parameter by which to judge whether something is an element or not.  With Pluto, we didn't have a clear cut definition for what a planet was until the IAU decided on the most recent definition.

We do have a good definition for element.

Besides, using half-life would not be consistent with a cut off at element 92.   Neptunium, Plutonium, and Americium all have Isotopes with half-lives that are longer than the longest lived isotopes of a number of elements with atomic numbers less than 92, the shortest being Americium at 7270 yrs. Compare this to Actinium, Radium, Francium, Radon, astatine and Polonium, The longest lived isotope in this group belongs to Radium at 1600 yrs, and the longest lived isotope of Francium (atomic number 87) is a mere 22 min.
Why include it as a "real" element while rejecting higher numbered elements with more stable isotopes?

159

Chemistry / Re: Why do we add elements to the periodic table that decay instantly?

« on: 20/10/2016 02:40:02 »

Do these new "elements" which last only for seconds or microseconds, exist anywhere else in the Universe, except in laboratories on Earth?

If not, I agree with Luke, they're not real "elements" at all. Just something we've fiddled about with, and cooked up locally.  Surely the fact that they disappear so quickly, rules them out as real elements. How can something that vanishes in a split-second, be regarded as anything more than a terrestrial artefact.

Shouldn't a real element stay around for the duration of the Universe, so that it could always be found in the Universe, without relying on a terrestrial source?

Many "Natural" elements do not have infinite lifetimes.  Carbon 14 is constantly forming being formed in our atmosphere and decaying, Uranium is also a "naturally" occurring element which decays, and in doing so creates other short-lived elements. I don't think it makes much sense to say that naturally occurring Radium is not a "real element" just because its most stable isotope has a half-life of just 1600 years.   
As far as these other element existing elsewhere in the universe, If we can make them here on the Earth, then surely they are formed in the supernovae that forged all the other elements including the Uranium we still find in our own crust.   
That's one reason for trying to make these elements on Earth; to learn the rules that determine just what is possible in terms of element formation and to verify whether or not our understanding of what these rules are stand up to experiment.