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Physics, Astronomy & Cosmology / Re: How fundamental is time?

« on: 15/01/2019 15:35:03 »

Chiral, you write :  " If "time" had been going more slowly before, then light emitted longer ago could appear to have lower frequency "  But I'm not sure relative what? light?

Then light need one invariant 'clock rate', or 'wavelength/Frequency' that then gets manipulated by this otherwise 'universal time change' you're wondering about, wouldn't it?
=

Or you're thinking of early light then being misinterpreted as it reach us in 'fast time'?
I'm not sure, but it's a interesting idea.
=

Let me translate it to this. Isn't that the same as to suggest that 'c' is a variable of sorts, although at all times keeping its 'proportion' relative all frames of reference, meaning that 'c' is 'c', both then and now. Seems a hard thing to test.

The second one (misinterpretation by us now in "fast time") is how I am trying to think about it.

I am definitely struggling with what it would mean for time to change. Would the frequency of the light shift as well, keeping up with time, and ultimately giving no difference? How can I reconcile this theory with the photon's point of view, in which its journey is instantaneous?

I think I am out of my league!

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Physics, Astronomy & Cosmology / Re: How much oxygen do you need for a return journey to mars?

« on: 15/01/2019 14:50:51 »

With recycling, you only need enough oxygen to assure a 20% content in the volume of breathed air. If they are breathing without masks, then the volume of the rooms within the spacecraft need to be filled to 20% with O₂. For instance, if the ship has only one room, with a volume of 600 m³, and is kept at a pressure of 1.0 atmospheres, you would need roughly 735 kg of air, about 150 kg of which would need to be O₂ (the remainder being N₂). If they have oxygen masks, one could use far less. Of course, that would require the ability to recycle the air at the same rate as it is processed by the people on board (scrubbing CO₂ will be at least as important--O₂ levels are safe as low as 18% or so, but if CO₂ levels rise up to 2%, the astronauts will be very uncomfortable!)

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Physics, Astronomy & Cosmology / Re: How fundamental is time?

« on: 15/01/2019 01:10:04 »

Consider a photon to be an object with zero mass. Some of those reaching us now, were launched umpteen billion years ago, so they don't exist for zero time!

I don't think you understood what I meant.

If I understood correctly, you had said something along the lines of, 'why is zero time any harder to understand than zero mass?' To which I responded, 'that analogy is not quite right: An object existing for a length of zero time is not that same as an object existing at t = 0"

Do you see why I differentiate between the usage of time as it pertains to the duration of an event or existence, and the usage of time as it pertains to a location of an event on a timeline?

Something that has the property of zero mass, is analogous to something that has the property of zero volume (not analogous to being at the origin of a spatial coordinate system), and is analogous to something that has the property of zero duration (not being at the origin of a timeline).

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Question of the Week / Re: QotW - 19.01.14 - Do trees eat soil?

« on: 14/01/2019 18:19:24 »

water and carbon dioxide from the air are the raw materials that account for most of the mass of a tree.

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General Science / Re: Are there aliens made of lava?

« on: 14/01/2019 16:09:42 »

Certainly the chemistry involved would need to be incredibly different from anything we currently understand as life.

But I think that none of the requirements you bring up would be impossible, or even that far from reasonable.

Structure/macromolecules:
There are incredibly diverse ranges of silicate-based structures, each based on different arrangements of SiO₄ tetrahedra. ( see here for more info: http://butane.chem.uiuc.edu/pshapley/Environmental/L27/1.html )

silicate.gif (36.92 kB . 532x698 - viewed 184 times)

And many of these structures are stable in the molten state. ( https://www.jstor.org/stable/99416?seq=8#metadata_info_tab_contents )

Metabolism/heat:
It is important to remember that it doesn't necessarily (and probably wouldn't) generate enough heat to keep itself molten in an environment like ours. Just as we cannot metabolize fast enough to maintain our 37 °C in an atmosphere at –180 °C. At the temperatures needed to keep silicates liquid (say 1500–2000 °C), there are still plenty of reactions that could reasonably create heat, or even be pushed uphill (like photosynthesis). (And who knows what pressures would be involved...)

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General Science / Are there aliens made of lava?

« on: 14/01/2019 14:56:47 »

I'm not sure where to put this (and I wouldn't be offended if this thread were moved to New Theories). I recently watched an excellent youtube video about Saturn's moon, Titan:

I realized that we would be “lava aliens” on Titan—where cryo-volcanoes release liquid water (with dissolved species, like salts and ammonia), which freezes back into ice at the surface, creating domes and other geological features almost completely analogous to our own volcano-dominated landscapes. Our body temp would certainly be high enough to boil their lakes (liquid methane and ethane) and melt some of their "rocks" (many of which are composed of water ice or heavy hydrocarbons, like benzene). We would need to bundle up to keep ourselves from freezing to death.

Likewise, we could imagine molten silicate-based life forms, from much hotter places (maybe even inside the earth???) which would need to bundle up quite warm to keep from freezing to death on our surface. They would instantly boil water, and could melt our rocks. Would they consume lava from volcanoes as we would water from cryo-volcanoes on Titan?

Many have previously discussed the possibility of silicon-based life, some recognizing that higher temps might be involved.

I wonder what sort of chemistry would be involved in such life forms...

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Physics, Astronomy & Cosmology / Re: How fundamental is time?

« on: 13/01/2019 19:56:07 »

@chiralSPO I am impressed! What exactly are your thoughts on a connection with the Hubble shift? Are you assuming a connection to the convergence of α and t? Also, what started you down this path?

I am still trying to see if it fits (or show that it cannot be, which is equally useful, but a little less interesting...)

I started down this path because I wondered if the apparent expansion (current and ancient) and big bang both could be explained in a way different from the currently accepted model. Questions like "what happened before the big bang?" can be answered more easily as "nothing" because the big bang would be an infinitely long period (in α time), which is identified only by how different the α and t values are. The concept of "rapid inflation" immediately after the big bang could potentially be reinterpreted as a period of time for which α and t were very different.

If "time" had been going more slowly before, then light emitted longer ago could appear to have lower frequency, even if there isn't any expansion (ongoing or ancient). This model could account for red shifts: ∂t/∂α < 1 for all α (and all t), and ∂t/∂α increases monotonically, so as α (or t) increases, so does ∂t/∂α. However, this model does not account for accelerating expansion (indeed, it was designed to converge such that α = t for sufficiently large values, and assuming that we are in that sufficiently advanced region). There are ways to tweak this model, but of course, once we start adding parameters in willy nilly, we can make a model that will reproduce anything...

I am not optimistic that this model will turn cosmology upside down, but I am interested to see how far this line of reasoning can go before it fails theoretical or experimental tests.

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Physics, Astronomy & Cosmology / Re: How fundamental is time?

« on: 13/01/2019 19:36:05 »

So back to the question: how fundamental is time? As I see it, it is as fundamental as the other dimensions, none of which requires an absolute frame or origin. If we consider mass to be "that which is subject to gravitational attraction" then zero mass is no more conceptually difficult than zero length or zero time - no need for an origin or any embodiment of negative mass.

Or am I being too naive to see the problem?

I would certainly not say you are being naive.

I liked the analogy to mass at first glance, but after some thought, I am not sure it is a good one. In my mind (happy to be shown wrong), an object with zero mass would be more akin to an object that existed for a duration of 0 time, or that had a radius of 0 length. However, unlike mass, both space and time appear to be descriptors of location within spacetime (I am open to discussion of mass-spaces, but that may require another thread...)

Our own perception of time is quite unusual, and certainly prone to mistakes. That we have found ways of making devices to measure it certainly has helped a lot, but I still do wonder if we are correctly interpreting what they are measuring. I will use another analogy that involves mass: we perceive weight directly, and it was quite an advancement for society, when it was realized that weight is not a fundamental quantity, and instead is a function of mass and our gravitational environment. My question regarding the fundamentality of time is along the lines of asking whether time is more mass-like (fundamental) or weight-like (can be distilled further).

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Physics, Astronomy & Cosmology / Re: How fundamental is time?

« on: 12/01/2019 08:03:10 »

thanks yor_on, there is a lot to digest there, and I want to think more before I respond to your post.

As far as the function I posted earlier, it appears to be one of a class of functions that will all meet the criteria I had posited earlier.

t = log_β(1 + β^α) meet all of the criteria, for any β > 1

As β increases, α and t become more similar to each other (converging at lower values of α (or t))

For instance:
If we evaluate with the natural base, e, then α and t converge to error < 1ppm by α = 12
If we evaluate in base 10, then α and t converge to < 1ppm by α = 5
While if we evaluate in base 2, then α and t converge to < 1ppm by α = 17

Again, one must be aware that we don't know what the units of α and t are... is this 17 seconds, or 17 quintillion years?

Speculation: Is there a way to fit to z values of Hubble shift to see if instead of expansion, it's actually this deviation? This might help us nail down what β is and what the actual fundamental units of time are?...

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Plant Sciences, Zoology & Evolution / Re: Plants on Steroids ?

« on: 12/01/2019 04:02:17 »

I don't think that steroids are likely to do much for plants. Many of the hormones that animals use for regulating growth are steroidal, but that doesn't mean they will work on plants.

However, plants DO have growth hormones, they just aren't steroids. Auxins and gibberellins are the two classes that come to mind (though it has been a looong time since I learned about these...)

https://en.wikipedia.org/wiki/Gibberellin
https://en.wikipedia.org/wiki/Auxin

These will control how the plant grows, but I doubt that they would make a venus fly trap stronger...

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Physics, Astronomy & Cosmology / Re: How fundamental is time?

« on: 11/01/2019 20:55:03 »

If we take f(α) to be -1/α then at α = -∞ we have our zero value. You stated that a value of 1 for time was a consideration. At α = -1 we have our value of 1. All negative fractions from α = -1 and approaching zero give an infinite positive sequence that can map to time. Infinite time then terminates at this α = 0 boundary. Crossing into positive α then gives us negative time which descends back to zero. You still have a discontinuity.

Indeed... t = -1/α will not fit the necessary criteria.

Is there a function t = f(α) for which:
• t is strictly positive for all values of α (t > 0)
• limit of t as α → –∞ = 0
• limit of t as α → +∞ = α (I know this would be t = α = +∞, but I want α and t to nearly converge well before +∞)
• the function is continuous for all real values of α (–∞ to +∞)
• an algebraic solution for f^–1 can be found: α = f^–1(t)
Ideally this function would also be differentiable everywhere (probably would have to be to satisfy the above constraints, but if not, I will still consider solutions that are not differentiable everywhere, but still adhere to the above)

I think that t = ln(1+e^α) works!
(I found it by realizing that the derivative of the desired curve followed a sigmoid curve, going monotonically from zero to 1, and that therefore the integral of a sigmoid would have the desired properties.)

t = ln(1+e^α)
• is continuous and differentiable and strictly positive across all reals
• limit of t as α → –∞ = ln(1) = 0
• limit of t as α → +∞ = ln(e^α) = α
• has the inverse function α = ln(e^t – 1)

Thank you to Bill S for reviving this thread, and to jeffreyH for prompting me to revisit the math!

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Physics, Astronomy & Cosmology / Re: How fundamental is time?

« on: 11/01/2019 20:04:42 »

I’m comparing time with inches and miles.  The real comparison should be between time and length (distance) on the one hand, and (e.g.) seconds and millimetres, on the other.  Thus, time by association, can be considered as a dimension.

This is how I understand it to be.

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Physics, Astronomy & Cosmology / Re: How fundamental is time?

« on: 11/01/2019 16:50:14 »

Change and time are not equivalent. Time is a dimension, and change refers to differences within one dimension.

This is most well defined within calculus (sometimes called the math of change), where the symbol ∂ (sometimes d) is used to denote microscopic change, often relating the change of one thing with respect to the change of another.

In this way, we can define instantaneous (microscopic) change of position along a spatial dimension (x) with respect to instantaneous (microscopic) change in time (t) as ∂x/∂t which is equivalent to the velocity in the x direction.

Although time is a very common dimension (variable) to compare changes against, it is not the only one. For instance we can look at the change in altitude with respect to change in forward distance traveled ∂y/∂dx (slope) or the change in cost of making chocolate with respect to the change in the cost of labor ∂$_chocolate/∂$_labor etc. etc.

What I am trying to learn in this thread is whether our concept of velocity (or any other rate of change with respect to apparent time) is best described as a ∂x/∂dt, or if there is a more fundamental variable (I believe I called it α earlier in the thread) such that ∂t/∂α is well-defined, and ∂x/∂α holds up better to the boundary condition that the big bang appears to impose on ∂t.

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Physics, Astronomy & Cosmology / Re: how do objects heat up in a vacuum? aka black holes

« on: 10/01/2019 02:04:44 »

zero entropy is at absolute zero or sub absolute zero.

Not quite. If we consider a system with fixed volume and fixed number of particles, then temperature is inversely proportional to the rate of change of entropy with respect to the rate of change of internal energy.
  T = 1/(∂S/∂U)

What this means is: iff (iff means if and only if) the temperature is positive, then entropy increases as the energy of the system increases, whereas iff the temperature is negative, then entropy decreases as the energy of the system increases. Lasers are a common example of systems in which the temperature is negative--as you put energy into the laser, it becomes more ordered, and then becomes less ordered when discharged.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/temper2.html

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Physics, Astronomy & Cosmology / Re: how do objects heat up in a vacuum? aka black holes

« on: 09/01/2019 16:53:26 »

My understanding is that the intense heat generated in accretion disks is due to collisions between particles with drastically different relative velocities. 

EDIT: Oops! Crossed with Kryptid!

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Physiology & Medicine / Re: What could cause a too high potassium count?

« on: 09/01/2019 01:51:59 »

Obviously cooking won't make extra potassium appear out of thin air.
I think that cooking just makes the potassium more easily available by breaking down the cell walls.
Or it could be that the reported numbers don't account for loss of water during cooking. I could imagine 100 g of veggies cooking down to 90 g due to evaporated water. Thus 100 g of cooked veggies would have about 11% more potassium than 100 g of raw...

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Physics, Astronomy & Cosmology / Re: How remiss is our attitude towards entropy?

« on: 08/01/2019 13:19:16 »

There’s another point from  "Does time stand still in the quantum world? I think is worth a mention".

Imagine four coins that can be either H or T. At regular intervals a coin is selected at random, and flipped such that it has a 50/50 chance of being H or T.

If the system starts out HHHH (the lowest possible entropy for the system), then after the first flip, entropy has a 50% chance of increasing and 50% chance of staying the same. Eventually the system will reach a state of maximal entropy, and can then only decrease or stay the same. Ultimately, as this game continues, the system will oscillate through all possible states with all levels of entropy (with each of the states essentially being favored by entropy).

This is great as an analogy, but like the frequently encountered deck of cards analogy, it can easily give a wrong impression.

Just changing the position or orientation of macroscopic objects from an arrangement that we define as orderly, to one that we define as disorderly doesn’t necessarily change its entropic state.  Does turning a coin over alter the number of  microstates accessible to its constituent particles?

Of course, the act of flipping the coin involves an increase in entropy, but this change is inherent in the "flipper", not in the coins as individual objects, or as a group.

Discounting the change in entropy of the universe caused by the action of flipping the coin, we can still determine the entropy of just the system defined by the coins.

There are 2⁴ = 16 possible states

There is only way to have four heads: HHHH
and analogously only one way to have four tails TTTT

There are four ways to have three heads HHHT HHTH HTHH and THHH
and analogously four ways to have three tails TTTH TTHT THTT and HTTT

then the remaining six states have two of each
HHTT HTHT HTTH TTHH THTH and THHT

so, after 10000 flips, it is most likely that there are two of each, and only a 1/8 chance that they are all the same (1/16 HHHH + 1/16 TTTT)

This system is still small enough that there isn't a huge difference between the highest and lowest entropy states. But if we had 1200 coins, or as someone else pointed out in the other thread, 10²⁴ coins, then there is effectively zero chance that the coins would all have the same arrangement, once allowed to evolve from the lowest entropy state for a few turns.

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Physics, Astronomy & Cosmology / Re: How remiss is our attitude towards entropy?

« on: 07/01/2019 22:17:38 »

But back to the point of this thread,

Another way to think about entropy is asking the question: what is the smallest amount of information I (let's be honest, not I, but some sort of demi-god) would need to describe the system perfectly?

One might be able to come up with an enormous data table that includes the instantaneous position, momentum, velocity, acceleration, and all other moments for each particle in the universe, as well as every interaction between each particle. Even if the universe were finite, this would still be an inconceivably huge amount of information, whether the whole universe were a giant perfect crystalline lattice at absolute zero, or the hot mess that it actually is. The trick is that in the former case (the cold crystal), many of those data points are redundant. If every unit cell within the lattice is an exact copy, then we only need the information to describe a single unit cell, and then info on how many identical units there are, and what their arrangement is. Therefore it is a low entropy system.

One way (not necessarily correct) of thinking about how the entropy of a system increases, is that as time goes on, each of those particles gains history, which is somehow encoded into the whole system. So even if all of the particles are identical, their positions, velocities etc. have changed based on the sum of all of their interactions to date. Thanks to conservations laws we still can describe the total amount of energy or momentum or charge etc. with single numbers. But once we care to see how that energy, charge and everything is distributed within the system, then we need lots of extra information.

The thing that blew people's minds in the mid 19th century is that they realized that purely deterministic views of the universe couldn't capture this apparent increase of information. Because if it were perfectly deterministic, then one need only define the starting state, and how much time had elapsed--meaning that the state of the universe at every point in time would have to have the same entropy... which they could experimentally prove was not a realistic model.

It wasn't until QM came along that they were willing to relinquish the deterministic picture (and even still there were and are some holdouts)

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Physics, Astronomy & Cosmology / Re: How remiss is our attitude towards entropy?

« on: 07/01/2019 21:48:57 »

Thank you for pointing out my dyslexic condition out to me,  I think your wrong about points two and three though. I will attempt to catch my spelling mistakes but never I never promise anything. Please provide documentation for supporting your position. below are mine.

"Following the second law of thermodynamics, entropy of an isolated system always increases for irreversible processes. The difference between an isolated system and closed system is that heat may not flow to and from an isolated system, but heat flow to and from a closed system is possible."  plenty of wiggle room there if you accept the expansion of Universe as irreversible.

If Entropy were decreasing, that would prove that the universe is not a closed and isolated system. However, there are many examples of open systems with increasing entropy (like the cup of coffee on my desk into which the added cream is dispersing). Therefore, establishing that entropy is increasing in a system does NOT establish that the system is closed.

the cosmic radiation background of the Universe's temperature is remarkably consistent. This to me, maybe not to you, presents an ordered system.

To me this suggests that the whole universe is the same age, and that expansion has been constant across it. This may be an indication of order in some way, but it is not apparent to me.

An ordered system presents as a constant stable rate of entropy.

Entropy is not a process so it cannot have a rate. Entropy IS disorder, so an ordered system has less entropy than a more disordered system.

The IF in my first statement places all that follows as a hypothetical question as to what would cause an increase in universal entropy in a closed system. If a system is constant and ordered its entropy is constant and ordered.

I don't know what this means... (see above for what entropy is)

An expanding Universe is increasing in entropy,

I'll agree with you there.

and you may wish to disagree with me ... but a catalyst is require to change the rate of entropy in a constant system. So, what catalyst caused the a constant stable thermal Universe to accelerate in conjunction with an increase in entropy? Its a simple question.

As I mentioned above, entropy is not a process, so we can't talk about the rate of entropy. If I assume that you mean the rate of change of entropy, we still still don't need to invoke a catalyst. Increasing entropy is the nature of nature. So I don't see what the question is.

or and u mis-spelled misspelled, do have dyslexia also? lol. 

Too bee fare, yew gout me their. Butt inn cases four witch won word wood mean x, and the other why, won out too bee specially carefree.

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Physics, Astronomy & Cosmology / Re: How remiss is our attitude towards entropy?

« on: 07/01/2019 18:59:37 »

If entrophy is increasing universally, it is proceeding to equilibrium. This implies that Universe is a closed system. In an expanding, closed system, a catalyst is required to speedup/increase entrophy. What do you propose that catalyst would be?

First: it's entropy, not entrophy (I wouldn't point it out if it were a lonely typo, but it was mis-spelled in every instance of the word in the previous post)
Second: increasing entropy doesn't imply a closed system--though we typically define our universe to be closed anyway...
Third: No catalyst is required for entropy to increase, even at an increasing rate...