Search results

In this video Richard Dawkins talks about a hypothetical situation and attributes behavior of birds to genetic changes. He goes on to say both fishing and piracy are unstable by themselves and an evolutionarily stable strategy is one when none can do better than the other. Isn't it the same case...

Yes, I agree with all the above. But my question is are these activities of humans part of evolution? She was arguing they are not. Disregarding those environmental forces which are not under human control, the cultural forces are again from the variety of traits of human genes fighting for...

Can you tell me how it can be justified if not entirely unjustified?

How is that an excuse? These traits might be more severe in those who do the destruction and you may not be inclined to do such things because your genes may not carry these traits. The population which is able to outlive and reproduce is going to spread those specific characteristics to its...

Me and my friend were talking about human activities. She said that humans are creating pollution, killing so many animals creating an imbalance in food chain, global warming etc. In short we are making it worse for ourselves and other species. My reply was whatever humans do is a part of...

Yeah..I thought the light is flashed from the elevator itself. But thanks for clarifying

No, the beam is not going to end up lower. If the elevator is moving at constant speed then it means it is at rest per se.

Thank you all. I think I kinda get it now. Thanks again

Yeah I believe this is the case. But not sure if it is as simple as this because a ball will have an upward velocity from the elevator which is not the same as in the case of a photon An inertial observer will not see any curvature. It will be a straight line for him. It is the non-inertial...

Thank you. I now understand (logically) light emitted from an elevator hits wall at the same height in that elevator and not everyone in other elevators can expect it to hit their own walls at the same height from their floor. Otherwise there will be infinite reference frames where light strikes...

This where I have trouble understanding why the guy in downward elevator can't expect the light to hit the wall at the same height from his floor. Because when the light was fired by the upward elevator, both were at same level and the photon just fired horizontally to both elevators at that...

Sorry to start this again but Let's say another elevator/earth moving down at constant velocity and the moment light is flashed, all are side by side at the same level. Now the guy in the downward elevator will expect it to hit the wall at the same height from his floor as it was fired but it...

Wow. That was clear as crystal. Thank you.

I am not sure if I understand that. Let me clarify my assumptions. Let's say I am in an accelerating elevator (upwards) with a meter stick on two sides of them standing upright and i flash a light from the top of one to the other. I will observe the light to hit the other some where below the...

Are you saying that the path of the accelerating elevator itself is bent from inertial standpoint?

This may be a basic question but why does light ray bend in accelerating elevator but not in one with constant velocity. I know a frame of reference with constant velocity is indistinguishable from a stationary one from the inside but I feel like like somehow the light seems to know whether it's...

I have a rudimentary understanding of evolution. Simply put it starts with chance and guided by natural selection which is not random. This is my understanding as of now not sure if its correct. In this video http://bigthink.com/videos/mankind-has-stopped-evolving-2 he says humans have stopped...

thx all for your replies! haha...very funny:rofl: by this http://en.wikipedia.org/wiki/Timeline_of_historic_inventions i see the number of inventions are exponential for every 3k years...does it mean people are becoming exponentialy intelligent?ofcourse that's just a speculation!

if the first known human fossil is 200k years old why the earliest known human civilisation is just few thousand years old? Why there was no reasonable developments for a very large time like 190k years?

In the distant past at bigbang the universe was very hot and dense. Can i say it was dimensionless then? If so did it come to this 3 dimension through 1 and 2?a little more speculation... is/will it go to higher dimensions?

i agree to that. Btw any idea why this became defunct? and any where is the further investigation carried upon?

does it imply an inclination towards telepathy cos i see Einstein quoting a physicist about that.any one?

yes i was about to ask about that. does this mean anything? though i dint understand most of observations stated there http://www.princeton.edu/~pear/pdfs/1997-correlations-random-binary-sequences-12-year-review.pdf

thanks for that link i was rofl :rofl: hearing the reason.too bad this video is not going to be popular among the masses i wonder if mainstream physics can survive the battle of natural selection :rolleyes:

i am stunned. Is there any credible source out there in media btw?

what does that mean?they are cheating people to earn money? btw I see both of them in guinness record

today i saw it on discovery. also saw a man with similar ability called by them as 'human stun gun' who knocks out people without touching them. seriously i am confused :confused:

lol! Yes i want to know if its really possible? i don't have any evidence other than what i saw on TV what made me worry is i couldn't brush it aside as it was shown in one of the prominent channels "history tv" (would they really make money showing some scams?)

i recently came across stan lee's superhumans in which a man claims to have telekinetic powers. Although i couldn't believe most of the super human abilities shown atleast i could convince myself they were possible under established laws of physics. But this one clearly threw me away. Earlier i...

consider A and B particles synchronizing clocks. Immediately after that B flies off at high velocity at the same time A flashes light perpendicular to B's motion. It hits some target c. Now in A's frame the event happened after t_{a}=perpendicular distance/c. But in B's frame it happened after...

if i were to leave Earth travel in as straight a line as possible with constant velocity eventually i would return to earth. is mine a valid inertial frame?

is it safe to say that all galaxies were 1 during bigbang and were teared apart as time went?if so isn't the rod which you use to measure is tearing apart right now?hence the length varies. the article cited by Naty did seem to explain this but i find it ambiguous i am unable to convince...

i don't understand. Gravity held matter together billions of years before but it dint stop the universe from expanding. When i said today and tomorrow i dint mean it literally. (say the difference between the lengths of 1 m today and after 10 billion years) if you are not sure what we are...

so does that mean we can't imagine how it would be?

is there any analogy to describe that model?

thats a brilliant question (atleast for me) i had a similar doubt in this thread https://www.physicsforums.com/showthread.php?t=566430 however i dint understand ghwellsjr's sol given over there. bobc2's explanation looked ok

a)since universe is expanding is today's 1 meter different from tomorrow's 1m? b)since distant between any 2 points is increasing is the universe expanding into 4th dimension?

bobc2, this is almost like what i asked for in my previous thread https://www.physicsforums.com/showthread.php?t=566430 but i have a doubt if there is only one time axis for all the observers they would age the same after separating and re-uniting isn't it?you can easily prove this by...

thats spooky!but on this i would say we can never ask the question "why" in this model because you will always answer "because that's the 4-d object in the path you just traversed" also does spacetime diagram really depict what's happening in the 4-d world. i mean if there is only one time...

As time is considered the 4th dimension can we say the 3-d world to be floating(advancing forward in time) in the 4D. If so is every inertial frame has is own velocity rate(moving in the time dimension) in the 4-D. When you have 3-D world if you want to bring 2 objects in contact you can bring...

Δt' is NOT the time measured in S'. It is measured in S as the time taken between consecutive ticks for a clock placed in S'.

ok let's restrict ourselves to frame S and don't jump to S' when we discuss.Let S(stationary) and S' (say velocity=0.8c) have identical light clocks and time between consecutive ticks is 1 second(meaning in any inertial frame, the frame ages by 1 second for each tick in a clock placed in that...

an apparent misunderstanding between us. can you explain your stand?

no you don't get me. Consider this a stationary observer S and a moving observer S' having identical light clocks. Now let S measure the time Δt between 2 consecutive ticks of the clock in S. Now how does he see the same clock to tick in S' (time difference between 2 ticks in S' as seen from...

i never denied a person at rest ages slowly when seen by a person in motion. i just took one of the 2 cases. may be i should have mentioned Δt' is the time taken for the event in S' according to the S clock.

yes... but i mentioned B is my FoR

why not?what i meant is this (an example) consider A moving at 0.86c and B is stationary. Now B has to wait for 2 years in order to have A 1 year old but he himself ages 1 year in 1 year (of course B is FoR) sorry about that!dint know

by convention Δt is the measure of change in time and t is of time at an instant. when a moving clock S' reads t' and stationary S reads t then t'=t\sqrt{1-V^{2}/C^{2}}(of course FoR is S) If an event takes Δt in S it would appear to take longer when happens in S'(seen from S) hence if Δt' is...

a quick question why can't 1-way speed of light be measured?

how can time run slow and become infinity?time ceases at light speed. btw your equation is wrong https://www.physicsforums.com/showthread.php?t=511170