Travel Definition and 995 Threads

Homework Statement Jaime is outside playing with her dog, Skip. She throws a tennis ball at an angle of 60° with an initial speed of 10.2m/s and from a height of 196cm. If Skip was standing beside her when she threw the ball, how far would Skip have to run in order to catch the ball just the...

So, I'm certainly not a physicist but I think I've just about started to grasp the concept of relativity and spacetime - maybe. A little bit. Hopefully. Anyway, I've always felt the concept of time travel is ridiculous, or at least backwards time travel, and I was trying to prove this to myself...

So imagine your on Earth at a latitude of 30 to 45° N, between two rotating Kerr Metric Blackholes with detached event horizons (dual singularities) allowing you to be shielded from the crushing force of the black holes. Which way do the rotating black holes need to rotate for the past and...

Hiya, I'm working on a 2D turn based space combat game, and I'd like to nail the mathematics of how a ship would truly move in space. Without going too much into my control scheme, here's the problem I'd like to solve: "Given a ship at point (x_0, y_0), with initial velocity V, along with...

I haven't been out of my city in a long time and I just recently started to get a wanderlust feeling. Traveling out of the country is too expensive, so I decided that I'm going to take a trip to some city I've never been to before and just explore it and all the stuff there is to do there for...

Hello PF, I come to you from the airsofting community with a question that has plagued much of the community for years. I hope to get some feedback from the physics community to help direct or debunk some of the "theories" floating around this issue. So, airsoft is a sport where...

Homework Statement Given the distance from the sun to Earth xE, the distance from the sun to venus xV and the mass of the sun m calculate the time delay due to gravity in receiving a radio signal sent from Earth to venus (and reflected back). Ignore the gravity fields of venus and earth. Venus...

Relativity is a truly fascinating and interesting subject that I don't fully understand. I'm currently in the process of studying it and this idea popped up in my head. This is just pure speculation from my side, which I expect to be wrong. I'll now try to explain the foundation for my...

((Wasnt sure where to post this one, but i felt this spot was good)) Okay Dr. Stephen Hawking conducted a time travel experiment in an attempt to prove that time travel will be invented one day. The basic idea was to throw a party for time travellers and announce the time and location of the...

Hello Everyone this is my first post on the forums and I want to share my ideas on what FTL is how it would possibly work. Now first thing is that I choose this part of the forum because of what FTL would involve. Now I am 14 who greatly interested in mechanical and electrical engineering and...

Hey! I have a problem that I have no clue how to solve. So I was hoping you guys could help me. I'm not from an English speaking country so I apologize. Homework Statement A thing is made to travel in water and on land. In water it travels with 20 m/s speed but on land with 25m/s speed. The...

Does sounds travel upwards? Why?

I am a writer of science fiction and I need to know some basics about space travel. I've read that it would take a ship 40 years to travel 1 parsec (3.26 light years) if the ship moved at 10% the speed of light. Does that sound right? Given that a futuristic ship could travel at this speed...

Homework Statement You and a friend decide to determine the radius of the Earth. You synchronize watches; then your friend drives 50km due west, at latitude 40°. Each of you determines the time when the Sun lies due south -- on the meridian Your friend observes the Sun to be on her meridian...

So from an electromagnetic source, will the photons travel "forever" or will some of them "collapse" after a while ?

From what I understand, space (not matter) can expand at a speed faster than that of light, and when it does, it goes in all directions. Would it be possible to create a controlled expansion of space behind a vehicle along a single path, like a corridor, that would change your position in space...

Why does gravity effect objects as fast as light. For instance, if the sun suddenly disappeared, Earth would continue orbiting the place the sun left for 8 minutes, which is the same time it takes light from the sun to reach us.. i think this might be some sort of standard speed in the universe...

If it is true that when traveling close to the speed of light makes you go forward in time. Then do you go back in time (observed from the destination) as you travel to your destination close to the speed of light? And why don't particles traveling at near light speeds appear to warp time...

Does electricity travel through vacuum?If so ,is it a good conductor?What is its resistance.

An electron moves from 0.93c to 0.99c in 0.819 x 10-11 s. Does this mean that the particle travels a distance of: x = (0.99c-0.93c)(0.819 x 10-11 s) m?

hi, i was wondering, for a black hole, as everyone knows,the escape velocity is greater than light. this means that the information about the existence of the black hole in terms of light never reaches the observer. so if the black hole were the cease to exist at an instant of time, the...

The energy required by a fish swimming at speed v to travel a distance L>0 in a current of speed u>0 is given by E(v) = aL((v^3)/(v-u)), v>u where a>0 is a proportionality constant. a) Find the speed of the fish which results in minimal energy expenditure. b) Give a qualitative sketch of...

Hi 'body, ok, this is a well known issue, but i still can't find a valid explanation of why FTL implies time travel. I've read lot of explanations, and each one ends up with a nonsense telling something like "if you drive a FTL car when you'll arrive you'll see yourself opening the car door...

Quoting from Wikipedia: "Time dilation would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. That is, the ship's clock (and according to relativity...

Homework Statement Consider the ODE x' = x2 + ε, where ε is a small number. Find the time T = T(ε) it takes for the solution to travel from x = -∞ to x = ∞. Let T1 = T1(ε) be the time it takes the particle to travel to x = -1 to x = 1. Show that T/T1 → 1 as ε → 1. Homework Equations...

Light's "direction" of travel, bending, and speed Hoping someone can clear up a few questions... At any particular instant in time (from anyone's perspective), is light (or a photon, if that helps) thought to have a specific direction of travel while between emission and absorption? I've...

Okay, so I'm no physicist, but I just had a random thought. So they say that traveling at the speed of light is impossible because the mass of the engine would have to be constructed infinitely big. But what if the propulsion didn't come from the spacecraft ? I was wondering what you guys...

Dear Physicists, Do you know why there was a massive fuss made last year about the experiments at CERN which recorded neutrinos traveling faster than light speed? Do these results contradict any previous experiment? I hear a lot of talk about said results conflicting with the equations...

Why when water is absorbed by something does it travel? I think it may be due to finding a lower energy from surface tension but I don't have any intuition of it. Thanks!

Calculating the optimum angle (resulting in the minimum time) for a linear-pathed spacecraft (unaffected by gravities) to leave a planet performing uniform circular motion to reach another planet undergoing uniform circular motion. I am really struggling to work my head around this problem...

I just got done watching Stephen Hawking's Into the Universe episode 2, which is about time travel. They think that time travel into the past is most likely impossible simply because of paradoxes (go back in time, and kill yourself before you went back in time). However, tiny wormholes the...

A UFO is observed just above the surface of the Earth moving at a constant velocity. An astronaut on the moon (3.8 x 10^8 m from earth) observes the UFO just above the surface of the moon 2.0s later. From the UFO's reference frame, how long did it travel from the Earth to the moon? The...

Would time travel to the past be possible if...? We didn't focus on reversing time itself (which is obviously impossible), but focused on accessing a past parallel universe. And creating some sort of portal to these past parallel universes, like a "quantum" wormhole (i know it sounds like...

It is well-known that associated with the Kerr solution which represents a rotating black hole, there can be a region of space-time where there are loops in space time (non simply connected paths which are navigable in principle). If this is so, it breaks causality and permits time travel in...

Hi Friends! Consider an Ideal condition. suppose, I prepared a device which can generate and vary the frequency of a wave (you can consider the wave to be electromagnic wave). Using this device I studied following two scenarios: 1. I created a wave having frequency between 1014 to 1015 Hz...

Hi, I'm not sure if this is the right sub-forum because i know very little about this kind of stuff :/ But something has been bugging me for a while and it's probably very stupid but like i said, I know very little :) So, from what i understand if we can travel close to the speed of light we...

I tried to find an answer to this here, but may have missed it. There must be a flaw in my understanding here, since it seems to be contradictory. Mass times the speed of light squared = Energy, and yet (according to Einstein), nothing can travel faster than the speed of light? I'm just...

I'm not native English speaker so some words or phrases I say maysound strange and awkward but I hope you could get over it...according to Einsteins special theory of relativity space is relative, tiem is relative but spacetime is constant...lets say that you're traveling constant is 300...

Homework Statement I have a twin brother, and we're 30 years old. If i travel for three years at 2.55 X 10^8m/s (0.85c) while my brother is a rest on Earth, how much older than me will my brother be upon my return?Homework Equations t=To/√1-v^2/c^2 [b]3. Try to work out To=3 T=? V= 2.55 X...

I am having trouble understanding how special relativity reconciles the concept of causality. In one frame of reference event A may be followed by event B, but in another frame of reference event B may occur before event A. In the first frame of reference an observer may claim that event A...

HELP PLEASE! I have to create an object that will travel a straight, horizontal zipline of 7.4 meters, and then travel back .4 meters to the starting point.. The object has to be all mechanical (no electric power source) and can't weigh more than 2 kg. It also has to be pretty cheap ($50) to...

Homework Statement Eduardo the samurai toaster was out for an evening stroll and went 120 m due north then turned and went 72m due west. Find the magnitude and direction of the dog's displacement. Homework Equations a^2+b^2=c^2 The Attempt at a Solution sqrt of (72^2+72^2)=...

I have been reading Einsteins Relativity and a simple concept in special relativity is tripping me up. I have heard that an object can never reach the speed of light. To which observer is this speed limit seen by. I know your answer will be "By all observers" but that is what I don't get...

Assuming a spacecraft had a propulsion system and sufficient fuel, what stops it from reaching the speed of light and beyond if a constant force is always being exerted on it? And in the event that it can go beyond the speed of light, will time distortion take place, and the crew on board...

[/SPOILER]Homework Statement T camper went 80m in the direction of 30°. He then turned and traveled 110m in the direction of 160°. Finally, the camper walked 42m at 195°. What was the camper's displacemnt Homework Equations sqrt{Rx^2+Ry^2} The Attempt at a Solution Rx 80cos30...

Let's say you take two metal objects, one black and one white. Out in the sun, the black will reach higher temperature in a given period of time. Now, let's say I take two glass jars. One is of DARK glass (like, an apple cider or wine bottle), and one is clear. In the clear one, I place...

1. Can a human travel to distant stars? If the faster you go the slower the time passes for you, then you could technically travel to stars several thousands of years distant from you. It could take thousands of years for someone on Earth, but just a few days for you. 2. Why can't we travel...

What is the reason for this?

I am an Electrical Engineering.I want to ask that how different signals move in a cable without effecting each other..e.g interference etc.. I am not strictly speaking about it interfence but how at the end we can differentiate these signals and get one of our need.

Hi everyone, I'm studying Motorsport Engineering and am trying to do an in depth analysis of a vehicle double wishbone suspension system. I have been using Excel to model the behaviour of certain aspects, and I am currently trying to analyse the effect of a wheel hitting a bump and it's...