Travel Definition and 995 Threads

How long/what distance would it take a spaceship (with a hypothetical propellant-less engine) to accelerate to near light speed, and secondly, how low long/what distance would it take to decelerate back to zero again?

Homework Statement Hello! This is an elementary problem, but I somehow can't compute it. How long does it take light to travel in: (a) 1.0 ft (report answer in nanoseconds) (b) 4.5 billion km, the average separation between the sun and Neptune (report answer in hours and minutes) Here is...

Homework Statement .[/B] A model steam train engine has a mass of 2.3 kg is powered by a sterno and white gas mixture that heats a small boiler. Once sufficient steam pressure is produced, the train is released from rest. The train travels along a straight and level track. At any time after...

Hi everyone, I am looking for any available experimental data which models off-road vehicle travel in clay and measures tyre and soil parameters. Parameters I am looking for include pull, torque, shear strength of the soil, sinkage, slip and deflection. If anyone knows of any available raw data...

Homework Statement A 0.35 kg particle moves in an xy plane according to x(t) = - 11 + 1 t - 6 t3 and y(t) = 19 + 3 t - 8 t2, with x and y in meters and t in seconds. At t = 0.7 s, what are (a) the magnitude and (b) the angle (within (-180°, 180°] interval relative to the positive direction of...

Homework Statement The sound speed in air at 0 degrees Celsius is 331 m/s, and for temperatures within a few tens of degrees of 0 degrees celsius it increases at the rate 0.590 m/s for every degree celsius increase in temperature. How long would it take a sound wave to travel 150 m over a path...

By Newton's first law of motion, every object will continue to be in state of movement or rest, until acted upon by external force. Now, why can't a rocket continue to travel after it was initially thrusted (do not know if its right word) by fuel ? like a satellite that is set in orbit with some...

In Kip Thorne’s “Black Holes and Time Machines”, he outlines objections to using traversable wormholes, if they existed, as time machines, the main one being (roughly) that radiation could also time travel, and mount up to destroy the wormhole. But isn’t another objection the conservation of...

Homework Statement John and Fred are racing. Fred, being faster, gives john a 20 s head start. John runs at 12 km/hr (10/3 m per second) and Fred at 16 km/hr (40/9 m per second) How long after John starts will Fred catch him? How far from the start do the two meet? Homework Equations d =...

What if we built an electromagnetic track around the circumference of the moon? We could then accelerate a spacecraft to a very high speed. In theory it would only be limited by the strength of the materials holding the craft to the track and the centripetal acceleration that the craft/people...

So I had one idea. Let's say that you have a cube, it's mass is 1kg and you travel forward in time 10 years and bring it back. Now you have two cubes. Then you go forward again, this time 10 years - 1 Planck time into future. Then bring that cube back again. You can repeat this infinite number...

I asked myself, "what did I have for breakfast tomorrow morning", my answer, " I don't know, haven't ate breakfast tomorrow yet", so, how can forward time travel be at all possible if future events have not happened yet?

I've read that faster than light travel is possible if we manipulate the space around the craft, but the energy needed is on the order of the sun's output. So, even if not practical, since theoretically it is possible I want to ask what happens to our destination's time. As I understand at...

A friend of mine is doing a science-fiction project involving the dwarf planet Eris and wants to employ scientific accuracy. He would like to know, given the orbits, when approximately would be a good time to leave Earth to travel to Eris (using our best current space-travel technology), anytime...

Hello and first of all I would like to say that I appreciate your work here since I am new to this forum. So here it goes. I was wondering for a long time. Someone travels back in time somehow and let's say he goes 1000 years back. He knows the future and he makes an action to change it. Our...

Shock wave is caused by the disturbance of air by the airplane. When it propagate the mechanism should be the same as that of longitudinal sound wave. Why sometimes it can travel faster than sound? (also see: http://physics.info/shock/ )

I suppose I am not the first to notice this, but if you are going at say, 0.999c you will have shrunk by a factor of about 20 and everything else on the craft. Suppose the spacecraft is 2000 meters long, at 0.999c it will shrink to about 100 meters long. So suppose a person 2 meters tall...

As far as I know sound is vibrating matter. Does that mean it could not exist in a vacuum? In outer space there is much less matter for sound to interact with so my question is, how does a sound generated in high matter places change as it travels to low matter places? For example, if you...

My physics professor told us something about interstellar travel, which I have a question on. He told us that scientists figured out a way to send objects into space and frequently increase velocities. He said they do this by sending probes and aiming them at planets and large bodies in space...

If you square both sides of the gravitational time dilation function for non-rotating spherical bodies, do you not get a "time travel function" that allows you to travel back in time with a massive enough body like a black hole?

http://i.imgur.com/UNrCRD0.png How can I calculate k1,travel2 & k2,travel2 in this system? I know that k_series = k1*k2/(k1+k2) but that is the extend of my knowledge.

This is as far as I've got so far but I think I'm stuck. These bosons are inside neutrinos and they go near the speed of light. The half life of these bosons (lambada) is 3*(10-25) s The speed of light (c) is 299 792 458m/s So I did this c / 3*(10-25) = 9.993081931m/s I just don't have a good...

I haven't been able to figure out how to approach this. It is actually a real-world problem.but I have simplified it a bit to make it easier to explain. A container with helium gas of pressure Pc in it is located in some environment where the surrounding air is at a pressure is Pe and...

Is it allowed to travel to the past in ST?. I've always thought about paradoxes in the regular framework (4D space-time). What about ST framework?. I need a little guidance here. Thank you in advance, AGZ

I'd like to hear another explanation.

It would seem to me that if you fly from point a to point b following the rotation of the earth, you'd have to go faster than this rotation to move forward. For example, if the Earth spins at 1,040/mph, then wouldn't a plane have to go faster than this just to escape the spin of the earth? I get...

Disclaimer: I am an aeronautical engineer with a background in fluids. My knowledge of cosmology only extends to articles and things I read before I go to sleep. So, here is my question: I have though about time travel, as many other people have. Currently we think it may not be possible, as it...

If the universe had stayed the size of a baseball, would it have taken light 13.5 billion years to travel across it?

Riddle me this. If it was possible to vibrate at near the speed of light, would that still create the effect of time passing faster for you but your surrounding passing through time at the same rate? Just wondering. I am aware that A) Time travel backwards would not function, due to the...

Hey all, So I've been writing a hard science fiction novel and need real answers from someone who understands the fields better than I ( I have no formal education outside basic high school classes in physics) The problem I have is I'm not a fan of faster than light travel but I need a way for...

Homework Statement An electron enters a solenoid at 65 degrees below a solenoid. The solenoid has a 10 A clockwise current is 33.0 m long and has 400 turns. Ignoring end effects what is the shortest amount of time in which the electron pass through the solenoid? Homework Equations Only one I...

I was looking at Time Dialation a bit today and some of the experiments with it. Considering time goes approximately 1/3 as fast as normal, under 100% the speed of light, what would happen if you went past the speed of light with a craft capable of warping. Would it have no effect due to the...

Hi everyone, many (sigh), many years ago, when I was in high school, I recall a little discussion we had with some classmates, which I gave little thought to at the time, but thinking back to it now, could never really figure out. It was about relativity. The story was that nothing could reach...

I'm wondering, I always hear how particles in the LHC collide with huge energies, and I'm wondering: how much energy is needed for particles to collide? I mean, if the energies in the LHC are huge and the ones in the RHIC are less huge you have to be able to do it with even less energy, right...

A massive star has a huge gravitational influence far far away from itself. It goes Supernova. Does the gravitational effect it has on its most outer objects still remain until the change in gravitational attraction has reached them at c? If so then does the gravity indeed travel in waves?

Homework Statement To prove that system will travel freely upto 180 degree m2 is counterweight and m1 is mass of pan (=3kg) i have attched the fbd or another link http://www.imagebam.com/image/54bb5a394377595 Homework Equations m1(h + a sin θ) g x = m2 y h g m2 = 9.13 kg The Attempt at a...

I've recently read a report about a group of Scottish scientists have managed to slow down the speed of light, not in a certain condition but through a special mask and the particles of light can be forever slowed down. Does that means the speed we need to achieve to make time travel is slower...

I'm new to all these concepts so sorry if i make any mistake in advance ! I watched a video on Nat Geo a few months ago it was about time travel into the future which is quite possible. They talked of building a track that goes around the earth. A train would go around the Earth at a very high...

Homework Statement This is for a lab report. Research Question: Why does a yoyo fall slower when unraveled than a yoyo in free fall? I need to find the time it takes for a yo-yo to travel 1 meter (falling) while unraveling/unwinding. The height is 1 meter. r = inner radius (I'm not looking...

After doing my own research I would like to know if anyone can recommend a good Sci-Fi movies on mankind's first interstellar voyage, besides the movie 'Interstellar', which I have seen?

Is it possible to travel to parallel universes of many worlds interpretation of quantum mechanics?

In theorized travel to the past -- in particular with a closed timelike curve (CTC), why is it possible to only go back in time to the point at which the CTC was created? Questions related to this would be: 1) Can space curve into a CTC if it was not originally in a CTC? 2) How can we be sure...

This is wild speculation but wild speculation is fun; Do micro black holes bend space and time like their bigger siblings? Could you then use the curvature of time of such a micro black hole and a radio transmitter to send a message back through time? Regards, JDM

My SO showed me this on reddit and we had fun with it. If you were sent back to the early 19th century naked and alone how would you convince someone that you were from the future and not crazy? No tricks allowed (meaning you can't pull a raygun from your colon). Let's hear it.

Hi, I am writing a piece which involves interstellar travel to nearby stars (Epsilon Indi being the one I will use in the following example.) It will be via a beam/ sail craft accelerated/ decelerated by solar-powered lasers (and lenses along the route). The craft will use constant...

Hey guys I have an issue I was wondering if you could help me with. There was a book in my high school library about the theory of relativity and time travel. I'm trying to find it again but the fact that I don't have a title for it is making things difficult. (For the record I'm long graduated...

Is the distance too far and/or the trip too dangerous for inter-galactic space travel by aliens wanting to reach Earth?

I read that X-Rays cannot travel through water and I wanted to understand why. What happens when X-Rays and water molecules interact that prohibit X-rays from traveling within water?

So I'm looking to find the distance light has traveled since matter - dark energy equivalence. Assume dark energy dominance from equivalence. Space-time has flat geometry and Ω0m = 0.315 , Ω0 = 1 Thus: Ω0Λ will equal Ω0 - Ω0m= 0.685 ρ0m (1 + zeq)3 = ρ0Λ where: ρ0m = ρ0c * Ω0m and: ρ0Λ =...

I was thinking about time travel...this is what i came up with ----> lets say person A (age 20,year 2014) travel to the year 2024 and meets himself (A2, age 30).lets say a kills his future A (i.e A2) and travels back in time (which i know is not possible but then). Now A is back in 2014.After 10...