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Tell me Physics facts!

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Original post by Dima-Blackburn
Time travel into the future is possible.


How far into the future? I read somewhere that it is possible but only by like a hundredth of a second.
Original post by RoyalBlue7
E=mc2 E = mc^2

Strictly speaking its actually

E2=m2c4+p2c2 E^2 = m^2 c^4 + p^2 c^2

We still can't really do fluid dynamics... We've been trying for 200 years.
When in doubt, recur to the energy equations. They always work because energy is always conserved.
Original post by natninja
Strictly speaking its actually

E2=m2c4+p2c2 E^2 = m^2 c^4 + p^2 c^2

We still can't really do fluid dynamics... We've been trying for 200 years.


Without this equation, GPS would malfunction.
Original post by pencil_case
How far into the future? I read somewhere that it is possible but only by like a hundredth of a second.


There's no limit AFAIK. Depending on how close to the speed of light you travel, and for how long you travel, it can be 10 seconds, 100 years, 10,000 years, a million years, etc.
Original post by Dima-Blackburn
There's no limit AFAIK. Depending on how close to the speed of light you travel, and for how long you travel, it can be 10 seconds, 100 years, 10,000 years, a million years, etc.


How far into the future would you like to travel?
Original post by pencil_case
How far into the future would you like to travel?


Probably about 1000 years, but I don't think I'd do it since I'd miss my friends and family.
Original post by Dima-Blackburn
Probably about 1000 years, but I don't think I'd do it since I'd miss my friends and family.


Fair enough. I just really want a hoverboard.
Original post by pencil_case
Fair enough. I just really want a hoverboard.


Ha, we actually have a working hovering transportation system today: http://en.wikipedia.org/wiki/Shanghai_Maglev_Train

It's not a hoverboard, but it's something :biggrin:
Original post by Dima-Blackburn
Ha, we actually have a working hovering transportation system today: http://en.wikipedia.org/wiki/Shanghai_Maglev_Train

It's not a hoverboard, but it's something :biggrin:


That's so cool! Thanks for sharing that link :biggrin:
Original post by Chlorophile
Lots of physical equations use imaginary numbers which don't actually exist.

This is pretty weird. Imaginary numbers don't actually seem to make much sense other than their applications (which there are apparently)
Q: How do magnets work?
lol :P
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Andy98
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If it works you've done something wrong.
Original post by lerjj
Why didn't you link this to when Sheldon said that in the Big Bang?


Because it was from my general reading :biggrin:
Rubbing a balloon against your hair and placing it against a wall. A-level physics mate.


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This is not necessarily true. Most people make the same mistake here.

The key point is to distinguish between light-like particles and time-like particles. In the first case, E=γmc2 E = \gamma m c^2 , this holds for particles travelling along time-like trajectories. The latter formula can be used to describe both light-like particles and time-like particles. It is this confusion that often leads to questions regarding massless particles having no energy i.e. E=mc2 E = mc^2 , and m=0 m = 0 then surely this implies E=0 E=0 .

An interesting question here is the following. What energy-momentum relation would space-like particles be described by? You will find these types of particles have some very strange properties.

Original post by natninja
Strictly speaking its actually

E2=m2c4+p2c2 E^2 = m^2 c^4 + p^2 c^2

We still can't really do fluid dynamics... We've been trying for 200 years.
(edited 9 years ago)
Original post by pencil_case
How far into the future? I read somewhere that it is possible but only by like a hundredth of a second.

basically time travels slower the faster you travel, if you travel at speed u relative to an observer the the time you measure = t/sqrt(1 - u^2/c^2) I think where t is the time the observer measures I think
so like time is dilated and the closer to the speed of light you travel the more time is dilated
like its not really you're travelling forward in time but like your clock just ticks slower than someone elses clock who you're moving relative to
also like weird stuff happens when you have acceleration and like I think space time bends and stuff but we dont do general relativity till 3rd year so I dont know that much about that
Original post by WishingChaff
This is not necessarily true. Most people make the same mistake here.

The key point is to distinguish between light-like particles and time-like particles. In the first case, E=γmc2 E = \gamma m c^2 , this holds for particles travelling along time-like trajectories. The latter formula can be used to describe both light-like particles and time-like particles. It is this confusion that often leads to questions regarding massless particles having no energy i.e. E=mc2 E = mc^2 , and m=0 m = 0 then surely this implies E=0 E=0 .

An interesting question here is the following. What energy-momentum relation would space-like particles be described by? You will find these types of particles have some very strange properties.


You will also find that there is no consensus as to whether those particles even exist at all...
Yes, that goes without saying. If they were to exist, they would not travel through the physical universe as we know it (thus there existence is pure speculation). The point is that if we assume such particles do exist, what properties would they have, and could they interact with our physical universe?

Original post by natninja
You will also find that there is no consensus as to whether those particles even exist at all...
Original post by WishingChaff
Yes, that goes without saying. If they were to exist, they would not travel through the physical universe as we know it (thus there existence is pure speculation). The point is that if we assume such particles do exist, what properties would they have, and could they interact with our physical universe?



Well they do underpin several 'niche' corners of theoretical physics. Besides, for various theories that include them, they often have different properties anyway... (yay symmettry breaking...)
Not really true. It is questions like this that have led to huge breakthroughs in the standard model of particle physics (specifically the study of the higgs field). If you wish to read more about it, the wikipedia article on tachyonic fields is rather informative.

Original post by natninja
Well they do underpin several 'niche' corners of theoretical physics. Besides, for various theories that include them, they often have different properties anyway... (yay symmettry breaking...)

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