1

Just Chat! / Re: What useful things can be done in a forum post?

« on: 04/05/2021 22:42:43 »

Hi. I'm a newbie here just trying to learn what can and can't be done.

What useful things can be put into a forum post? 

Your LaTex seems to work just fine. You can also post pictures. There's a posting-tips thread pinned in general science.
Welcome to TNS!

Questions:     
      1.  Can I preview a post?  I've clicked the preview button at the bottom right and nothing happened.

The preview appears just above the edit window. You probably have to scroll to see it, but it works fine.

2.   Can I insert a small picture in-line with the text,  or do all attachments and insertions just get dumped at the bottom of the post?

See the tips thread for how to do this. Not trivial, but not difficult either. Posting an existing net image is trivial, but posting an uploaded thing takes a little work.

2

Physics, Astronomy & Cosmology / Re: Are galaxies bigger on the inside and galactic πs LESS than 3.14?

« on: 13/04/2021 14:20:06 »

The graphic is massively exaggerated, illustrating why it's probably not a good idea to get your science from social media. Except within the event horizon, a black hole bends space no more than the same mass that is not in a black hole. In other words, if our sun was compressed to a black hole, no orbit of anything would change and the only way we'd notice is:
"Hey, Who turn out the lights?" - proper Dave.

The black hole in the center of our galaxy is tiny and comprises less than 0.000003 of the mass of the galaxy. The bending shown in the picture is nonsense. Yes, they take bending of spacetime into account when computing orbits and such, but the effect is so negligible that it takes very fine measurements of something very close (S2) to the black hole to detect the difference from Newtonian orbital motion.

It has also been measured in Mercury due to the precession of the orbit, but S2 has I think a 17 year orbit and it takes a seriously long time to get precession numbers from it.

3

Physics, Astronomy & Cosmology / Re: Is time travel possible?

« on: 12/04/2021 01:45:17 »

Hi all
Halc can I please just clarify your points in regards to;

All clocks are affected by these things. Atomic clocks are in no way special in this way. Paint peels slower relative to a frame in which it moves faster.

In regards to your first point does direction of relative away/towards have any bearing

"Direction of relative" does not parse. If you mean direction of motion, the answer is no, it matters not. In SR, time dilation relative to inertial frame F is a function of your speed relative to F, and speed, being a scalar, doesn't have a direction.

The coordinate rate of clocks can indeed be negative given a non-inertial coordinate system.

are you stating rate of atomic clocks as negative as going in reverse or just slowing down ?.
Because if negative = reverse

I meant reverse. We're talking about a coordinate effect, and one can create a non-inertial coordinate system where some clocks run backwards. Look up the Andromeda 'paradox' as an illustration of this.

are we not setting the scenario of the paint analogy going from peeling/flaking into the wind to.  returning to the painted surface becoming shiny and new then liquid in the brush/sprayer to been back in the paint tin ?

If my coordinate system orders the paint events that way, then yes. It's just a coordinate system.

4

General Science / Re: Does ginger help with travel sickness?

« on: 08/04/2021 00:19:17 »

Ginger is known to calm the stomach. Somebody with a better biological background might better be able to explain how it does this.
Ginger ale (soda flavored with real ginger) and ginger tea also help with motion sickness and general stomach flu symptoms.
I've never heard of it being particularly effective against a hangover, which typically hits you in the head and not so much the gut.

5

General Science / Re: Why are Tennis Balls hairy or fluffy?

« on: 05/04/2021 20:32:39 »

Then the dog runs off eagerly into the distance, seizes the ball in its jaws, and runs back, tail-wagging, to present you with the returned ball.

Your dog maybe. With some, getting the dog to let go of the thing is quite an exercise.

Anyway, the point is - dogs seem to like "retrieving" things.

Some are specifically bred for it, just like some for tracking, ratting, herding, pulling, etc. Each breed has these traits bred right into them leaving the dog uncomfortable it not put in a position to exercise these inborn instincts.
So I'd say it very much brings happiness to the dog to retrieve the bird, stick, tennis ball, or frisbee.

So couldn't dogs be employed on tennis-courts. To do the retrieving?

Doubtful. Don't retrieve until the play is dead. Don't defile the ball, rendering it unusable for another point. Don't fetch a ball best fetched by a closer dog. Exit the court with ball ASAP. Don't leave puddles, drool or otherwise.

Do they reuse balls for multiple serves?  In baseball, the ball is often taken out of play if it has ever made significant contact with either the ground or the bat. They go through a lot of balls. Tennis even more so if they don't reuse them.

6

The Environment / Re: What would happen if all of humanity vanishes in one second?

« on: 29/03/2021 18:18:19 »

The survivors obtain it from the millions and millions of metal coins left lying around in the debris of the old, now extinct civilisation.  The old coins - the nickels, dimes and quarters, get "mined". Then hammered and beaten into new arrow-heads.

It's a long time since I read "Earth Abides", and my memory of it has faded .  However I do seem to remember that one of the characters in the book - was it "Ish", raises objections to this method of "mining".  On the grounds that it's not the true creation of new artefacts from raw materials, but more akin to mere "scavenging".

Scavenging will definitely be prevalent at first, but it is limited. When this resource runs out, has enough 'civilization' been recovered to accomplish actual mining of new raw materials?  Thing is, our civilization has picked all the easy-to-get-to resources.  They'll not find fossil fuels to run their forges, so any new civilization that arises must be built on a foundation of more renewable materials.  Energy may well be attainable, but metals?  Where are they going to find that except by scavenging?

The USA was able to prevail in several wars (1812 war comes to mind) because it had all these resources (wood in particular) that had been stripped out by the more mature civilization of Europe at the time.  That advantage has now faltered since we've mined this continent down to the state of all the other ones now.

7

Physics, Astronomy & Cosmology / Re: Centre of the universe?

« on: 28/03/2021 22:52:25 »

Suppose the Universe started from a single, concentrated,  point, which contained all the matter in existence.
Then, for whatever reason. the point "exploded", and threw the matter out in all directions..

Just as, for example, when a hand-grenade explodes, and throws bits outwards in all directions.
If you observe these bits, and measure their trajectories, you can plot them back, and determine their centre of origin.

In a similar way, these days, we have telescopes of sufficient power to observe galaxies, and measure their trajectories, using Doppler effects.

So couldn't we use these, and other observations, to determine the centre of origin of the Universe.

I mean, if the Universe really did originate from a single point, why shouldn't we able to find where that point was?

Good question. Even in Newtonian physics you can't tell. If you were on one of those bits exploding from the grenade, all the pieces would appear to be receding directly away from you at a pace in proportion to its distance. Every point would appear to be as much the center as any other and there would be no obvious way to locate the point in space of the explosion. It would be completely dependent on the arbitrary choice of reference frame.
So in this sense, the explosion-from-a-point-into-empty-space model seems to generate the same observations as one with nothing really moving and space expanding uniformly.  But space is not expanding uniformly, and the sort of recession speeds you'd get from an explosion into empty space would not result in accelerated recession rates or in event horizons.  Only the FLRW model actually matches the observations that have been made.

A big example:
Suppose all the pieces (galaxies?) were the exact same size.  You're on one of the pieces of the grenade, looking at the other ones.  The nearest ones are not receding very fast, are still fairly close by and seem relatively large. (Andromeda subtends an angle 7 times wider than does the moon).  The faster it is moving away from you, the further it is at the time you look at it, and the smaller it appears to you.  But that's not what we see.  GN-z11 is the fastest receding object from us with light reaching us after about 13.4 billion years, so it should appear the smallest (assuming they're all the same size), but it isn't.  It subtends an angle far too large, as if it was less than 3 BLY distant when the light we see was emitted, not 13.4 BLY.  The thing is four times too large and appears larger than similar sized things with far lower redshifts. This is exactly as the expanding space model predicts since while the light might have been emitted at c from GN-z11 back then, but the space between us and it at the time was expanding at a rate of ~6c back then, so the light actually got further away from us at first until getting to space moving ever slower until it could finally make headway against the expansion rate.
That is a very different observation than one predicted by stuff filling space from a point somewhere.

Shortly after the big bang, inflation expanded space at a rate faster than the speed of light.

Expansion is not a speed, and thus cannot be compared meaningfully with one. The units are different.
Speed is measured in km/sec, whereas expansion is measured in km/sec/mpc

We would simply need better and better telescopes to see further.

The CMB is as far as a visible-light telescope is going to see because it isn't transparent. It's like trying to see through a brick wall. Can be done, but not with binoculars.

8

Physics, Astronomy & Cosmology / Re: Do Certain Astronomical Phenomenons Affect US?

« on: 26/03/2021 15:08:17 »

As the Moon is connected with Tidal effects onto the Earth...
I wish to know, do or would Tidal effects also affect a Glass of Water?

Imperceptibly, but yes.  As chiralSPO points out, it is not just selective to water since it is a gravitational effect. It thus deforms Earth's crust and bends trees and such.

Considering the human body is said to be approximately 60% Water on an Average..Can or Will or Does the Moon in anyway Affect it?

It has to do with mass, and yes, tidal effects have a trivial effect on any extended object like people. An object the size of a person in freefall will tend to align itself vertically due to tidal effects. It would take quite some time. On the ground, weight is the primary measurable difference.

Does the Water in the glass or inside off of Us Rise?

No, but the surface would not be a perfect segment of a sphere centered on Earth. Tides do not create more water, so the water in the glass cannot rise unless the tides are so strong as to suck it clean out of the glass.

9

Physics, Astronomy & Cosmology / Re: Do you believe in possibility of life in other galaxies?

« on: 23/03/2021 17:36:28 »

But still, there is a possibility that in some galaxy and in some exoplanet there are some forms of life or this planet can be similar to Earth in conditions for living for humans.

By the logic spelled out above, it is essentially a certainty, yes.
The beings living there will probably not be particularly human-like, but perhaps the chemistry will be somewhat similar such that we might be able to eat the local vegetables.

OK, so such a place likely exists. So what? We can't sense it.

If we only consider planets within our visible universe, less than 2.5% of them are within the Hubble radius, and far less than 1% of those are within 2 billion light years distance. So suppose somebody a mere couple billion light years away has fantastic sensing technology and notices Earth has the right atmosphere and environment for them.  They also have ships that can move at nearly light speed.  By the time they get here (4 G-year minimum), the Earth will be a charred smoking husk, certainly not the friendly environment they sensed from afar. Such environments are temporary. Maybe some life here has evolved to a hot dry planet, but it won't be what the visitors came here for.
So the existence of some planet habitable to us without modification is of little interest to humans even if we could somehow know where it is. It has to be reasonably close by.

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Physics, Astronomy & Cosmology / Re: Do you believe in possibility of life in other galaxies?

« on: 23/03/2021 13:52:41 »

With over a hundred billion galaxies in the universe.

There are considerably more than that, given the fact that there's no known limit to the size of the universe. If there is a finite chance of life in a given galaxy, then there being life elsewhere is a certainty.

some scientists claim that they have already found some exoplanets that can be like Earth.

Their idea of 'like Earth' is that it has gravity within 50% of ours and perhaps a likely temperature that is within 100°C of ours, each being one of the few things that can be measured of an exoplanet from our distance.

If they mean one that has free oxygen, that doesn't happen naturally. It only happens if there is life already there, and improbably similar to our kind of life. I notice most people that ponder this question (including many scientists) only consider Earth-like carbon/water based life. There are far more possibilities, but most so alien they are hard to conceive without finding (or even recognizing) it first.

11

Physics, Astronomy & Cosmology / Re: Are photons relative?

« on: 23/03/2021 01:07:28 »

What you are missing is the location of the photon at any given instant is not relative to anything else. All other particles are relative to the photon. That is why the speed of light is used in relativistic gamma. This is the absolute maximum speed limit. As an absolute it can't be reached by massive particles. Since everything else's velocity is measured in relation to this absolute then the photon must map to an absolute frame.

Photons do not define a frame of reference. The laws of physics are the same in any inertial frame of reference, but not in a photon frame since photons always move at c relative to any frame.  They cannot be at rest.
Photons do not define any particular 'frame' since while they may all have the same speed, they have very different velocities.

You seem to have stopped asking questions.
If you are asserting these things, then this topic belongs in new theories. If you're not asserting them, then read the replies and don't suggest that things are being missed.

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New Theories / Re: Can something move faster than speed of light?

« on: 22/03/2021 12:18:06 »

Rg = 2GM/c2

Well, R_s = 2GM/cē yields the Schwarzschild radius of a given mass M.

If the idea is somehow black hole related and by somebody who doesn't understand the mathematics himself, then what you need is a better understanding, not a prize.

Moving faster than c is easy.  Relative to the ECEF reference frame (the one GPS uses, in which my house is stationary), Neptune moves faster than c.  In the cosmological frame (the coordinate system used to map the entire cosmos, including the parts beyond the visible universe), GN-z11 (a very distant but visible galaxy) is currently increasing its proper distance from Earth at a rate of 2.3c. We see an old image of it when it was very young and receding at a much higher pace than that (like 6c or something).

13

New Theories / Re: What exactly is gravity?

« on: 21/03/2021 20:30:26 »

Why is it that You always Specify the Apple falling onto the Earth?

Why can it Not be the other way around...that the whole damm planet is rising up to catch the falling Apple?

Technically, both accelerate towards each other.

Under any theory, acceleration is absolute, as required by conservation of momentum.

Under Newtonian physics, both accelerate towards each other, but the apple accelerates much more than does Earth such that the momentum change of each of them is equal and opposite.

Under Einstein's physics, the ground exerts a force on the tree accelerating the tree away from the recently detached apple.  The apple doesn't accelerate at all, instead following a geodesic. An accelerometer on the apple would read zero g. The ground immediately under the tree (not the whole Earth) traces a curved path through spacetime due to the compressive net EM force being exerted on it from below. An accelerometer on the ground would measure that one g of proper acceleration.

So, could you say that whenever you walk through your front-door, into your house. the house and door are accelerating towards you?

In this instance, the house accelerating would result in a change of momentum that is not balanced by any equal and opposite change. It violates momentum conservation. No force can account for such acceleration.

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Physics, Astronomy & Cosmology / Re: Is there a better way to power a spacecraft than a nuclear source?

« on: 18/03/2021 17:00:38 »

As we can see the most advanced and the most frequently used propulsion system  for spacecrafts is nuclear.

Reference?

I may be behind the times with the news, but my current count of known spacecraft with nuclear propulsion is zero. I may be wrong about that, but calling such a low number 'most frequent' is quite a stretch.

Nuclear propulsion has been the subject of numerous research projects since the 50's, but none of those projects seems to have produced an actual spacecraft.

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Physics, Astronomy & Cosmology / Re: Inner and outer space?

« on: 08/03/2021 12:47:35 »

Thanks Halc, I've often thought that the enormous processing power of the human brain,  can't possibly be explained in terms of the crude on/off transistor switches that we employ in  our digital computers.

Neurons are effectively on/off switches of a biochemical sort. They fire or they don't.
A brain has 100 billion cells running at about 20 watts, and the largest CPU might have a sixth that many transistors running at a similar wattage, so brains are still more energy efficient.  The area of the chip is about 1/300th that of the brain, so the chip wins in terms of density.  It would probably take hundreds of transistors to simulate what a brain cell does, and hundreds of brain cells to simulate what a transistor does, so that just shows that a direct comparison isn't particularly meaningful.

But these effects are constrained by the vey simple nature of the transistors. Which are basically made of silicon, and not much else.

Nerve cells are more complex mostly because they have an additional task of staying alive. They're biochemical transistors of a sort which get their energy from combustion of chemicals instead of from the electrical currents.

Whereas our brains are built of organic molecules which far exceed transistors in atomic, and chemical complexity.

That's not a good thing. A simple thing doing a task is more desirable than a complex method of achieving the task.

This complexity may generate quantum operations on a very large scale.

The quantum effects enable the complex behavior, not the other way around.  A super-simple creature or transistor device (say jellyfish or transistor radio) still utilize quantum effects for their operation, but are in no way particularly complex. Complexity comes from scaling up the simple effects that quantum behavior enables.

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Physics, Astronomy & Cosmology / Re: How does mass-energy curve spacetime?

« on: 08/03/2021 12:07:12 »

If the Sun suddenly disappeared...it would still take around 7 to 8 minutes for the Earth to be spun out of it's Orbit.

It is not physically possible for the sun to suddenly disappear, so pondering the result of the impossible premise is meaningless. At best, the sun can be met with some calamity like exploding or being hit with a large fast fly-swatter that moves it away, but not faster than light.

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Physics, Astronomy & Cosmology / Re: Inner and outer space?

« on: 08/03/2021 03:21:23 »

Would digital technology even work, if electrons were smeared-out blobs.

Yeah, it would work just fine. The imprecision in their location and momentum is not so large as to render those technologies inoperative.

Digital technology and brain cells both actually rely on the imprecision in their location, hence both technologies would be rendered inoperative if electrons had classic location and momentum. Both (transistors and cells) utilize quantum tunneling to send signals across barriers otherwise insurmountable by the voltages employed.

18

Physics, Astronomy & Cosmology / Re: What makes it go Faster & Slower?

« on: 07/03/2021 22:22:05 »

What makes the Earth go Faster & Slower in Orbit around the Sun.

At any point not at Perihelion or Aphelion, the path of the orbiting thing is not tangential to the force being exerted by the orbited thing, and thus there is a component of that force that either adds to or subtracts from the current velocity vector of the orbiting thing. This changes its orbital speed.

This is especially noticed with coments or with rocks tossed from tall buildings, both of which go into very elliptical orbits and thus go faster quite noticably.  Unfortunately for the rock, it cannot complete its orbit becaue the ground often gets in the way, but it would be true if dropped from a sufficiently tall building.

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Physics, Astronomy & Cosmology / Re: Our solar system in relation to universe expansion?

« on: 06/03/2021 22:07:27 »

Acceleration is a Vector, meaning change in Velocity.
The Earth is Always Accelerating(falling) towards the Sun.
But there Is a minute difference in Velocity, Right?

Over a short time, yes, but it accumulates.  The centripetal acceleration of Earth due only to the sun is about 0.006 m/secē which means that after 2.8 minutes the velocity has changed by 1 m/sec towards the sun. After 6 months, the difference is about 60,000 m/secē, which isn't exactly minute.

So...Earth decelerating would make it fall(pulled back) towards the Sun with a greater force, hence change in Velocity

Deceleration isn't a physics term.  Changing the velocity of Earth without changing its distance from the sun is going to have no effect on the gravitational force between the two. Force is a function of the mass and separation of the two masses, but not a function of the motion of either object.

Deceleration cannot be considered as a physics term, simply because there is Nothing applying the brakes on Earth's Velocity..instead it's only the elliptical orbit that the Earth takes around the Sun due to which the Velocity decreases, Correct?

It isn't a physics term because it refers to scalar speed (which is ambiguous without a reference frame) and cannot specify a change in a velocity vector, making it's effect ambiguous. Deceleration is applicable to something like an automobile where it's frame of reference (the road) is implied and hence speed as measured on a speedometer can be meaningfully expressed as a scalar, and deceleration can mean a reduction in that speed.

20

Physics, Astronomy & Cosmology / Re: Our solar system in relation to universe expansion?

« on: 06/03/2021 16:41:29 »

I'm familiar with " Sphaggetification "...is that even a word?

Sphaghetification is listed in dictionary.com, but my spell checker still highlights it.  Yes, it's a very known term in the physics community.

Did You know the Earth accelerates & deaccelerates while moving around the sun in the ecliptical orbit

That's the dictionary definition of those terms, which is an increase and decrease of speed, respectively. In physics, acceleration is a vector and means change in velocity. The Earth always accelerates towards the sun due to the pull of the sun. Deceleration is not a physics term. Yes, Earth's speed relative to the sun varies throughout its orbit, and is currently decreasing from its maximum in January.
Fun fact: The moon always accelerates towards the sun as well, even when between Earth and sun. The pull of the sun is stronger, so the path of the moon does not curve towards Earth.