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Question of the Week / MOVED: indefinite integral

« on: 27/04/2022 12:57:04 »

This topic has been moved to Just Chat!.

https://www.thenakedscientists.com/forum/index.php?topic=84643.0

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General Science / At what gravity does a person run the fastest?

« on: 30/03/2022 16:23:37 »

The question came up given the realization that if one was on the equator of the moon, one could remain stationary relative to the inertial frame of the moon by running west at about 15 km/hr, which I can still do, albeit not for any extended time.

But I can run that fast here on Earth, not on the moon. Too little gravity up there, and hopping seems the idea method of locomotion up there, and we're not evolved to hop.

So given flat ground, normal atmosphere, and standard running attire (no shoes with wheels or springs), at what gravity (expressed as a fraction of g) can one run the fastest?  Too little and each step takes you airborne with a high probability of not landing on your feet, and with way too much air friction between bounces.  Too high and you'd barely be able to walk without breaking bones.

While we're at it, what sort of physiology has an optimal speed at higher or lower gravity?  Only ground-locomotion counts, not birds or fish or anything which utilizes the medium instead of the ground. I imagine ants could go faster in higher g, Maybe kangaroos would work better at lower g, especially if they could use their tail to maintain proper orientation in flight. They already go 50 km/hr (sustained), and in low enough gravity could probably outrun a cheetah (80, sprint)..

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General Science / MOVED: The Quest For A Universal Time Clock

« on: 16/05/2021 21:40:54 »

This topic has been moved to New Theories.

https://www.thenakedscientists.com/forum/index.php?topic=82308.0

It is full of incorrect assertions concerning existing theories, and shows no sign of inquiring about what science actually says about the subject.

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General Science / MOVED: Final evidence of a rigged election in 2020?

« on: 09/02/2021 19:39:15 »

This topic has been moved to That CAN'T be true!.

https://www.thenakedscientists.com/forum/index.php?topic=81643.0

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Physiology & Medicine / MOVED: Anti - Covid Hat Invented - I Fear No More Covid

« on: 19/01/2021 17:41:30 »

This topic has been moved to Just Chat!.

https://www.thenakedscientists.com/forum/index.php?topic=81467.0

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Question of the Week / MOVED: Can I take Zinc from filling pure zinc metal

« on: 16/01/2021 16:15:41 »

This topic has been moved to Just Chat!.

https://www.thenakedscientists.com/forum/index.php?topic=81443.0

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General Science / MOVED: Proof that the universe is an computer program double slit shot test proves thub

« on: 11/01/2021 14:16:30 »

This topic has been moved to That CAN'T be true!.

https://www.thenakedscientists.com/forum/index.php?topic=81402.0

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Physics, Astronomy & Cosmology / MOVED: New model of the Universe.

« on: 01/01/2021 17:25:30 »

This topic has been moved to That CAN'T be true!.

https://www.thenakedscientists.com/forum/index.php?topic=81336.0

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Physics, Astronomy & Cosmology / MOVED: The nature of light and the size of the Universe.

« on: 01/01/2021 17:17:06 »

This topic has been moved to That CAN'T be true!.
https://www.thenakedscientists.com/forum/index.php?topic=81337.0

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General Science / MOVED: A new matrix book

« on: 07/12/2020 17:51:55 »

This topic has been moved to Just Chat!.

https://www.thenakedscientists.com/forum/index.php?topic=81111.0

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Physics, Astronomy & Cosmology / MOVED: What causes Entanglement?

« on: 04/12/2020 23:15:03 »

This topic has been moved to New Theories.

https://www.thenakedscientists.com/forum/index.php?topic=81075.0

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General Science / MOVED: Is making infinite momentum into electricity sustainable?

« on: 26/10/2020 16:34:45 »

This topic has been moved to New Theories.

https://www.thenakedscientists.com/forum/index.php?topic=80818.0

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Physics, Astronomy & Cosmology / MOVED: Split: Bell's paradox: Does the string break?

« on: 13/08/2020 01:25:14 »

This topic has been split off the "Is angular momentum frame dependent?" thread and moved to New Theories.

https://www.thenakedscientists.com/forum/index.php?topic=80334.0

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General Science / How fast can new land be populated in the long term?

« on: 25/05/2019 02:11:17 »

I am putting this in General Science since it is a general question addressing many problems in several unrelated fields.  The premise is artificial, out of necessity, but the answer should be real.  The idea is to get you to think.

Statement of the premise:
Suppose the world is flat and indefinitely large.  Everything else is more or less the same as the way we know it.  Humans are confined to say a continent, but then let loose.  The rest of the world is filled with the same sorts of plants and animals that existed say 1000 years ago. There is day and night, and seasons, not particularly explained.  Gravity is continuous at any altitude (which is consistent with a flat object).  It's a little like Niven's Ringworld, except not round, and infinite.

The question:
At what long term pace would humans move into new territory?  The answer to that isn't as important as thinking of ways that would limit the long term pace.  You can take any technology with you, but you will need to refuel/replace any of it as needed. Positing infinitely durable toys is against the spirit of the question.

Obviously it can't just be one group of people like Lewis and Clark.  The lead people will get wiped out now and then.  Towns will need to be built to 'feed and breed', so to speak, and to support the 'front line' effort. One problem might be what incentive would be needed to keep up this effort indefinitely, but I think evolution would take care of that. A group of people genetically inclined to move at a greater pace will get there first and will be the ones to populate the lands.

Anyway, the idea is to come up with some aspect of the effort and see if it might be a candidate for the thing that most limits the pace.

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Physics, Astronomy & Cosmology / Does space expansion limit max length of an object?

« on: 16/05/2019 20:41:32 »

Continuing with my theme of long rigid objects, I wish to explore the limits physics puts on the length of a non-accelerating object.

Special relativity has no restrictions.  If I have an object of length X and am at the end of it, there is nothing preventing me from attaching another meter to it.  This is trivial, but the special relativity does not model the metric expansion of space, so quoting SR seems kind of useless.

General relativity does put restrictions.  For a constantly accelerating object, there is very much a limit to the number of additional meter sticks I can tack on to the trailing end of the object.  Doing so would be the equivalent of trying to extend a fishing line into a black hole and expecting the string not to break.  For an object just sitting there, does this limit apply?

I’d like to consider two models of the universe: Universe U has constant expansion with no acceleration, no dark energy.  Universe A is the one like we seem to live in which has accelerating expansion and dark energy, which I suspect might put a limit on our long object.  If it gets too long, stress is more than any force can overcome, just like the fishing line in the black hole.

In the non-accelerating universe U, where exactly are all events simultaneous with ‘now’ in a given inertial reference frame?  How far can we push the boundaries of an inertial frame?  Certainly not so far as to where the expansion of space has objects increasing their proper distance from us at a pace greater than light speed, but how are we going to measure the length of our object in the first place.  It seems important to define this first.

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Physics, Astronomy & Cosmology / What limits does relativity put on acceleration of long objects?

« on: 19/10/2018 12:54:07 »

This thread is meant to investigate relativistic limits on the acceleration of large objects.  To drive the points home, my objects will be large and fast, but never with impossible properties like being massless, infinite rigidity, or with instantaneous acceleration, all of which can be shown to violate fixed speed of light.

Consider a long object, say a light year in length, which is fairly fragile in that it will allow only negligible physical compression or stretching before it breaks.  Hence the force of propulsion is spread as needed over the entire length of the object. Our engines/rail-guns are as powerful as they need to be.

For slow accelerations, the clock at the front of the object will get ahead of the ones further back, so the acceleration further forward run is lower, but for a longer time.  If the rear acceleration takes 10 years (measured in local accelerating frame) to get up to say .866c, the front acceleration will take place for 10.866 years to get to that speed iff it ignites and ceases at the same time (object frame) as the rear acceleration.  The points in between can accelerate proportionally.  In this way, the entire object might be under acceleration at once, but only in the object's own frame.

That seems viable for only slow accelerations, and even then, in any other frame, part of the object is accelerating and the part of it not, so right there it seems on first glance to be putting strain on our object, but I cannot prove that since the two parts are always separated in a space-like manner, and so cannot directly effect each other.

Scaling up the acceleration demonstrates the limits if not the deficiencies of my proposed methods.  Clearly at some point there is strain the way I am doing it.  Is there a strain-free way of accelerating a long object?  More exactly, is there a way to do it that never changes the object's proper length?

There is proof of sorts that there is a correct solution, since if there is compression or tension somewhere in the object, we could compensate for that with a thrust function that applies more or less force at points further forward.  There must be a solution that involves zero strain, but even then the length of the object puts an absolute limit on the magnitude of the acceleration.

Edit:  There seems to be nothing impossible about near instantaneous acceleration.  Many of my examples assume as a limit an acceleration to a desired speed in negligible time.  If this is found to violate finite light speed or some other law, kindly post details since it will effect my answers for minimum time to get a big thing somewhere.

Update, Feb 2019:  I think I found that very violation.  See post 97.  Infinite acceleration makes the speed undefined, and without a defined speed, the proper length is undefined.  Acceleration can be arbitrarily high, but not infinite.