Jerry Schirmer

Austin, TX

Age: 34

I am a Ph.D. general relativist working as a software engineer. I like to still go and do physics as a hobby, and to keep up my skill and knowledge.

16h
revised Why are sine/cosine always used to describe oscillations?
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1d
revised Why are sine/cosine always used to describe oscillations?
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2d
answered Why are sine/cosine always used to describe oscillations?
2d
answered Do photons make the universe expand?
2d
comment Does water turn solid under deep ocean because of high pressure?
Look at the phase diagram above. While it is possible to melt ice by applying pressure, this is only true in a pretty narrow region around the triple point of water.
2d
comment Does water turn solid under deep ocean because of high pressure?
@Davidmh: any place likely to have enough pressure to solidify ice (i.e., in Neptune's core) is not visible.
Apr
18
comment Does GR really allow superluminal movement?
@Jim: what is relative velocity and what is expansion of space is coordinate-dependent.
Apr
17
comment Does GR really allow superluminal movement?
Note that global superluminal travel is allowed for paths that cross apparent horizons. These restrictions are on superluminal travel that allows for global round trips.
Apr
17
comment Does GR really allow superluminal movement?
@Jim: what you say applies to round-trip superluminal travel. But you can certainly have superluminal "relative velocities" invoking only ordinary matter. Consider our relative motion with matter outside of the visible universe, for example.
Apr
16
answered Can weakness of gravity explore new dimensions
Apr
15
answered 'Warp'- type travel; is it possible?
Apr
15
comment Wouldn't angular momentum of a binary star system decrease?
Also, note that the Hulse-Taylor curve is nearly perfect withouta accounting for any quantum effects: astro.cardiff.ac.uk/research/gravity/resources/hulse_taylor.jpg
Apr
15
revised Wouldn't angular momentum of a binary star system decrease?
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Apr
15
comment Metric for infinite straight cosmic string
Where is your fourth spatial coordinate?
Apr
15
comment Wouldn't angular momentum of a binary star system decrease?
Note that this is not definitive, as there are orbit stability effects from general relativity to care about, amongst other things, but this should be enough to show that these orders of magnitude combine badly.
Apr
15
answered Wouldn't angular momentum of a binary star system decrease?
Apr
14
revised What is the notion of a spatial angle in general relativity?
corrected christoffel symbol
Apr
14
comment What is wrong with considering the Atwood machine as a system?
@Shubham: if $m_{2}\neq m_{3}$, the center of mass of the system B moves relative to the pulley, so its net acceleration is $a_{0} + a_{cm}$. It is almost certainly easier to just solve this by doing free-body diagrams for all three masses, rather than having to worry about treating the internal system properly.
Apr
14
comment fusing two air containers with fixed pressures $p_1,p_2$ and temperatures $T_1, T_2$, what end-result $T$ and $p$ will be?
You need a second equation that expresses the conservation of energy.
Apr
14
revised What is the notion of a spatial angle in general relativity?
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