Travel Definition and 995 Threads

The time taken for a free-falling object to fall a set distance (on earth) is, according to Wikipedia, described by the equation: t = √(2d/g). Why is the distance doubled in this equation/ how is this derived?

if i throw a ball of matter forward in space will it travel faster than light given enough time and space with nothing what so ever to stop it i.e Newtons first law of motion in effect.i figured it should becuase it will have a force to give it a constant acceleration(change in velocity).my...

Someone started a recent thread with a statement that included "light exists outside of time". That excerpt was flatly rejected, and the post generated such a lively response that it was closed, having "wandered off into philosophy". It made me wonder if "light exists outside of time"...

Hi. I am a 13 years old and interested in particle science. I was reading on tachyons and how you could hypothetically send them as signals back in time (not that I'm saying we will manage anytime soon or ever). It got me think about it and I realized something. I'm sure somebody has heard about...

What do you think of the following scenario*? Aliens are future humans who discovered faster than light travel. They propagated throughout the universe. In so doing they traveled back in time, to our time, or even earlier times. *I read this in a popular space opera novel. It may have been...

I've heard a few times that information can't travel faster than C, but what if you have an extremely dense metal rod that extends for 1 light year in length, the moment you move it here, wouldn't it instantaneously move at the other end 1 light year away? Or would the electrons that make it up...

Greetings everyone, I asked my professor about this, recently. I had always heard that if you could gain the impossible amount of energy necessary to run beyond the speed of light, you would travel backwards in time. But he however, told me something that I have never heard before. He said...

I was listening to a podcast about the solar neutrino problem, and they discussed how we have deduced that neutrinos are not massless due to the fact that they interact with other particles (even if this interaction occurs rarely). I paraphrase: "a particle traveling at the speed of light is...

I've been told contradicting ideas about this. I've been told that light doesn't travel at a constant speed everywhere (i.e. light slowing down in speed after entering a more dense medium). However, I've also read that light speed is constant everywhere (i.e. if you could travel close to the...

Theoretically you can travel back in time by moving faster than the speed of light, or the universal speed limit. Is there a minimum speed? 0. But with gravity you would be moving, so if you move against gravity relative to yourself you are moving. So if there was a place in the universe free of...

Question: Sirius is about 9.50 ly from Earth. To reach the star by spaceship in 15.5 y (ship time), how fast must you travel? Answer in terms of "c". 0.4843c and 0.6129c are incorrect Relevant Equations and Constants: Attempt at solution: Can anyone help out I really don't know what...

So i was wondering...if you have 2 surfaces of different areas..one bigger and one smaller...and the one with a smaller area disperses light through a lens..does more light travel through the one with the lens or the other or does the same amount of light travel through both? To get further...

Homework Statement [/B] 1. Homework Statement A spacecraft is prepared to visit α-Centauri, which is at the distance 4.37 light years from the Sun. Provisions for the crew are prepared for the duration of 16 years. How fast must the spacecraft travel for this provision to be enough? Answer...

Hello all, i recently purchased a travel trailer, and i want to create a lift to get inside it. a little background on me, i was in a motocross accident, broke my back and am now paralyzed. I currently work at a full fabrication shop as a mechanical drafter, we have the capabilities to make...

I have a problem of the following picture. x_0, y_0, z_0, V_0, and V_1 are fixed. http://postimg.org/image/6r0ogcx3f/ The travel time is obviously t = \frac{1}{{{V_1}}}{[{({x_1} - {x_c})^2} + D_1^2]^{1/2}} + \frac{1}{{{V_0}}}{[{({x_c} - {x_0})^2} + D_0^2]^{1/2}} According to a high-profile...

How does light interact, and travel through Solid matter as matter gets thicker, in width.?In the absorbion, and emission process of light, hitting electrons, I do not really understand that much, about electron energy levels, and how they change when a lot of atoms become molecules, and them...

Homework Statement In the figure, a block of mass m is moving along the horizontal frictionless surface with a speed of 5.70 m/s. If the slope is 11.0° and the coefficient of kinetic friction between the block and the incline is 0.260, how far does the block travel up the incline? Homework...

Hi Folks, What is your opinion on this article? It suggest that interstellar travel is a fantasy. http://www.scientificamerican.com/article/interstellar-travel-as-delusional-fantasy-excerpt/# Yet, I read articles about institutions like NASA investing in various conceptual propulsion...

According to Einsteins Theory of relativity if an object traveled at the speed of light, it's mass would become infinite, time would seem to stop relative to others and it length would become absolute zero. The same conditions were thought of at the Big Bang, when time didn't seem to have...

So I was writing a short story and I came up with this scenario. Please pardon my Arrogance, but my theory uses several theories. I do have some sort of knowledge in Physics but here it goes. Could you, hypothetically transfer information in the form of gravitational waves between two entangled...

If an object is in a large vacuum chamber and is dropped, what is to stop it from accelerating to the point that it passes the speed of light, because there would be no air resistance to stop it from constantly accelerating?

Homework Statement For a modern physics class, has to do with relativity In a lab experiment a muon is observed to travel 800 m before disintegrating. The mean lifetime of a muon is Tau = 2E-6 s A muon's travel distance at the speed of light is x = tc = 0.66 km Earth's atmosphere is x = 100 km...

Homework Statement Hi, I'm currently studding a module on PLC and have a question on "what will happen if you do this ...". Homework Equations I don't have a problem with explaining operation of each rungs of the ladder diagram, I need some help on explaining the function of the reverse relay...

Hi, I'm currently studding a module on PLC and have a question on "what will happen if you do this ...". As I don't have a problem with explaining operation of each rungs of the ladder diagram I need some help on explaining the function of the reverse relay and travel limit switches. Can anyone...

A couple of questions around faster than light travel. 1. I don't understand why this implies traveling back in time (as is sometimes suggested). For example : A tachyon traveling at 150% c travels between Point A and Point B and back again. While it will arrive at Point B before it is...

Why does light (or indeed any object) travel the shortest path between two points (whether for flat or curved space/space-time) ?

Hello All, I only have a vary basic understanding of physical concepts so please bear with me. I'm an object with mass greater than 0, a maximum speed, a maximum rate of acceleration and deceleration. Suppose I want to travel from point A to point B. The path is chosen for me and it leads...

So, I have been designing a game that uses Lego models to create spaceships that you then maneuver on a floor and do battle with. And one of the goals of this game is to be as realistic as possible, within the limits of a 2D environment. With that in mind, I have created a system that...

Homework Statement A voltaic cell is set up and a chemical reaction proceeds spontaneously. Which of the following will not occur in this reaction? (A) The electrons will migrate through the wire. (B) The cations in the salt bridge will migrate to the anode half cell. (C) The cathode will...

(I apologize beforehand if I'm asking such an 'amateur' question , I admit that I'm not a physics student / physicist nor scientist / science student ,.. but , as just a 'normal ordinary' person, at least I am very interested in these things ,. and how I deeply wish Humanity / Mankind can 'leap...

How can Gluon travel at speed of light when it is bound inside a proton or neutron?

Homework Statement "Infrared light doesn't travel through air easily". Why is that? Is it because there are lots of molecules that absorb the energy so that a reaction occurs? Homework EquationsThe Attempt at a Solution

... compared to a opaque materials electrons. Is it the amount of electrons in the atoms shells ?If you have a four inch cubic block of glass, and carbon, light passes through the glass no problem, but the carbon will absorb some red, yellow, green, and blue light, but if you look at the carbon...

I always ask myself this question, and I think it is better to ask people that really know about this. Due to the impossibilities that Special Relativity poses, such as any object with mass not being able to travel at the speed of light. If we don't manage to at least scratch that speed, I...

Hello there, So I'm 23 years old, been passionately studying physics for some time now. Oh it's been fun and fascinating, I wouldn't trade it for anything. I could apply for my B.S. in physics any day now. I've always been great at physics. My conceptual understandings, my neat and unique...

Is it because that there are less molecules within one unit volume in rarer medium that light is able to travel through it easier?

Homework Statement Why can’t transverse waves travel through a gas or liquid? Homework EquationsThe Attempt at a Solution I understand that transverse waves require rigid medium through which to transfer their energy so they can travel through solids. I'll just accept that transverse waves can...

I am writing a novel about time travel and don't quite understand the theoretical science behind it. If I understand correctly, Einstein's General Relativity theory opened up the door for the possibility of time travel even though he dismissed the idea as impractical. Einstein proved...

I just had a flashback to an applied electromagnetic course I took a few years ago. I believe we were learning possibly about waveguides (maybe) or something, but there appeared a phenomenon in the math that made it appear as if the wave was traveling faster than C. When asked about it, the...

Hi, I'm new to the forum and have a maths question. So basically, X is the time axis (per minute) and Y is the price axis. I have a data set of 200,000 Y values in excel. If I were to draw two horizontal lines through the sine like wave, how many times will the line travel between A and B?? I...

I was discussing with a friend about speed of light and time traveling and I realized something bizarre. I could be wrong so please correct my mistakes. So let's assume we want to go to our alien neighbour whose planet is 100 light years away. When we travel there with near light-speed, we...

I am working on a project which involves air nozzles. I am interested in estimating the time it takes for air particles after they leave the nozzle to reach a particular distance away. I have the following information--- a converging nozzle, the speed with which it is coming out of the nozzle(I...

Hi! I've written a novel in which my main character travels through time (into the future) 18 years. While the concept of time travel is necessary to the plot, the details are not. Meaning, the book isn't sci-fi, but contains elements that wouldn't normally exist in a contemporary novel, so...

Homework Statement So there are two planets A and B whose centres are 6r apart. A and B has the same mass M and radius R. What is the minimum velocity(from the surface of B) of the rocket required to launch it from B so that it reaches A ? Homework Equations F=GmM/R^2 The Attempt at a...

Dear all, Let's assume I was planning an interstellar journey with relativistic speed. Being at rest on earth, the distance to the destination is ##d##. Let's further denote the proper time I will need to reach the destination as ##\tau##. Is there an official term for the effective speed...

Dear All, Is it possible to watch Earth orbiting the sun in space like we watch a car coming towards us on a highway ? I mean, I would like to see it coming towards my spaceship at the rate of say 50 km/hr. Now some questions - 1. What should be my location and speed of my spacecraft...

So off to Mars we go. But really how are we going to get there? The most expensive part of space travel is overcoming atmosphere. So you could say the biggest obstacle of space travel is Earth travel. It takes virtually no energy to cross space but it takes massive amounts to get into space...

traveling at the ~speed of light leads to length contraction. based on that wouldn't a 20AU path be shorter if traveled at speeds near the speed of light ?

Without taking into consideration any G forces or other phenomena's. So say we slowly and gradually speed up, eliminating any risks of G Force related issues. Fly in empty space without any obstacles in our way and will not be in our way in this scenario, and finally the spacecraft is...

Good day to you all, I have been reading Stephen Hawking's book "A Briefer History of Time" (yes, I'm a novice ;)) and I need some verification on if my understanding is correct regarding his theory/conclusion saying that if one travels faster-than-light, he would be able to travel into the...