Travel Definition and 995 Threads

So, I have been thinking about TRAPPIST-1 and how far away that system is from us. It is 40ly away from Earth, according to our frame of reference. This is often put in a way that makes one think that even at speeds close to that of light, it will take almost 40 years to get there. The muons in...

Hi guys, I am writing an undergraduate screenplay about physicist. The physicist is working on a mission with the aim to fly a spaceship with human crew to an extremely distant planet with an environment suitable for humans. Its really not that important for the story, because the film is...

I want to strap an estes b4-4 rocket to a toy car and calculate how far it would travel. What I know: Mass of car: 300 grams Rocket nominal force: 12.8 Newtons I think this means the rocket would accelerate my car for a=F/m = 12.8 kg * m/s^2 / 0.300 Kg which means 12.8 m/s^2/ 0.3 = 42.67...

Hi guys I'm finishing up some promo art for my original comic book. You're seein it here first. But its missing something- an appropriate equation. I would like to integrate a math equation into the art. I am attempting to depict FTL travel, using qualities similar to an LWFA, the plasma being...

if GR is correct about spacetime (expanding of space) then i think time travel in back (back to the past) is impossible... suppose before 2 billion years ago (from now) the total space (volume) of universe was "X" so, it's clear that the space (volume) of the present universe must be greater...

Homework Statement Muons of Kinetic energy 'E' are produced in collision with a target in a laboratory. The mass of a muon is ##106MeV/c^2## and its half life in it's rest frame is ## 1.4 * 10^{-6}## in its rest frame. what should be the minimum KE such that more than half of the muons...

I want to know what mathematical tools I would use in the event that we have the right technology. So far I have only calculated the distance to Alpha Centauri using parallax. I need any other tool: hypothetical speeds of ships, trigonometry, vectors, trajectories, any tool that is necessary...

Homework Statement A ship's engine supplies power of 85MW, which propels the ship of mass 5.3×106 kg across the sea at its top speed of 11##ms^{−1}##. The frictional force exerted on the ship by the sea is directly proportional to its speed. If it starts at top speed and then travels in a...

Do you believe it's possible to travel between our world within a different multiverse? If so, how do you believe it happens/is possible (e.g. Will we invent specialized machines or are there certain points/places that act as portals?)

Hello everyone, I have been trying to learn as much physics as my little brain can handle in my off time. I have to say this forum has made a world of difference helping me do so. I would like to throw a concept out there at the risk of being told that it's nonsense and fringe science...

Let's say we already colonized some of the planets and moons in our solar system. Mars,Moon, Europa and etc. Planets like Mars and other has less gravity than earth, so the resource needed for space travel in our solar system will reduce by a lot if we launch spaceships there. Say, that we...

Homework Statement Hello there physicsforums, I have a problem that I'd like feedback on as I'm not sure if I had solved it or approached it correctly. A ball that is traveling 5m/s is 30 meters above a person who is standing still. How fast must the person travel in order to catch the ball...

Hey guy, I was browsing YouTube and watched a speed comparison video and it was just different races timed. I noticed that light speed took 12 minutes to reach Mars from earth. So I thought this If we look at Mars through a telescope or what ever, Does that mean we are actually looking back in...

Dear community, I have no formal education in physics, but I think I have understood some of the basic concepts and ideas in SRT. I am currently trying to find a solution to a problem that came up during my reading of Joe Haldeman's "The Forever War", a Sci-Fi novel that deals with the impact of...

This is something I often read in news on established websites, and countless times more in different forums. It goes something like this: someone says that in order for us to be able to do something, we would have to reach distant galaxies. To which someone replies "Yeah, but unfortunately...

I have a question. If something stands absolutely still in the space can it time travel?? I mean can it fall out of this universe? I am not a Physicist and forgive me for my mistakes in English.(I am foreigner) Just a question.

I've been stuck on this physics problem for several years now. I would be very grateful if someone could explain how to solve this problem. The farthest a human could travel from Earth in one lifetime theoretically is limited only by the acceleration a human can withstand, and the length of...

Is it possible now that we can built a warp machine and put inside the spacecraft and traveling around the universe?

Homework Statement A star is 95.0 year lights away from Earth. How much time does it take to a cosmic ship, which moves with speed 0.96 c, to reach the star, if it is measured from a watcher from a) Earth a)ship c)What si the distance of trip, based on the viewer from the ship? Homework...

I'm trying to design some novel cross bow designs and also trebuchet's with the trebuchet (similar to catapults to those who don't know) using springs or a combination of weight and springs. I'm looking into using linear springs and pullies for the crossbow depending on whether they can be...

I realize that unobserved light it going to be difficult to measure, but could the double slit experiment be set up to give us an average air time for the particles? I find it hard to believe that a particle acting as a wave would travel at exactly the same speed as an observed one.

https://www.sciencedaily.com/releases/2012/10/121028142217.htm Usable or not this seems to be a spooky statement can this 10000 be falsified?. Experiments have already shown that if you want to invoke signals to explain things, the signals would have to be traveling faster than light -- more...

Correct me if I am wrong and pls answer to my question .The 4th dimension is also known as SPACETIME.Does it mean that if we if are able to understand it and if we apply it,we can travel space and time?If Yes then, will we be able to construct TIME MACHINE and travel through time?and also...

Homework Statement Two waves of light in air, of wavelength 550 nm, are initially in phase. They then both travel through a layer of plastic as shown in the figure, with L1 = 4.00 μm, n1 = 1.40, L2 = 3.50 μm , and n2 = 1.60. What is their phase difference after they both have emerged from the...

Hi:smile:. I am new here! My first question: We are watching those stars which were present many years ago in the sky. So, basically, we are viewing the past. Now, my question is that, if we develop some kind of technology through which we are on such a 'star' and are magnifying earth(just...

You think Hubble's deep field is seeing what happened 14 billion light years ago and not zooming into what is currently happening? With the trillions of suns in each galaxy why is there so much darkness within a galaxy let alone inbetween galaxies? If Hubble was stronger it would see farther. If...

So I have been watching COSMOS of late and in the 4th (I think) episode it states the possibility that other universes exist inside of black holes. I am aware of the immense strength of a black hole's gravitational pull so my question is this: Is there a material strong enough to resist it and...

Dear PF Forum, Before I get a NO answer, I'd like to ask a few question. https://en.wikipedia.org/wiki/Hubble%27s_law#Observed_values As of 13th July, 2016 Hubble flow is 67.6 km/s per mega parsec. Or 67km/s per 31 trillion * 1 million km or per 3.26 million light year. Say a galaxy 11.68 giga...

This paper states that extended space travel would be harmful for astronauts, how would future space travel over come cosmic radiation https://www.sciencedaily.com/releases/2016/10/161010052832.htm

Why does a bolt of lightning crackle into many different directions when it travels to the ground? Can a bolt of lightning be made to travel in straight direction, is it theoretically possible to understand and control lightning?

I need to figure out a gearbox ratio to get a 12 inch wheel to travel at 2mph. If I remember right the equation should be 1foot * 3.14*gearbox output rpm*60 then all divided by 5280 to get the final mph. Am I on the right path? Then I need a gearbox output around 58rpm. Thanks to all of...

Hi all, and thanks in advance. I am an old guy learning GR for fun. Reading Weinberg's "Gravitation and Cosmology". PhD in math 1998, so I read all books like I read math books: every character, every word, every line, every page extremely carefully. I am stuck on the stupidest thing. On p.72...

1.if we assume BIG BANG as frame of reference for time then how could one go to past ? 2.if i travel the time and go to past at the time of BIG BANG, at what place i will be? 3.why the speed of light is same for everything(moving or stationary)? 3.and what will be the apparent speed of light...

Why does this redshift versus lighttravel time equation work? z=-ln(1-t)/sqrt(1-t^2) where (z) is the cosmological redshift, and (t) is the look-back time where the present equals 0 and the origin of time equals 1. Ned Wright's cosmology calculator with the default inputs [H_o=69.6...

Hi, I'm a CAD student, writing a research paper for my English Comp. class on interstellar travel. I wan't to quote Einstein but can't find were he stated this exactly: Because space and time are relative, the faster you move through space the slower you move through time relative to someone...

If a guy gets on a rocket that travels at the speed of light for a finite period of time (in relation to other observers not moving at C) the guy in the rocket experiences no passage of time. In this scenario his leaving and arrival of the rocket happens at the same time in his frame, correct...

Homework Statement A falling stone takes 0.28 s to travel past a window 2.2 m tall. From what height above the top of the window did the stone fall? So from this problem I think I have these variables: vo = ? (or 0 because falling usually indicates 0 for an initial velocity?) yo = 0 y = 2.2m...

Not sure where the best place to post this is, but here it goes. Imagine you were sent back in time, far enough back when a lot of the now known scientific laws, rules equations etc, haven't been discovered yet. You're someone who is intelligible with many scientific fields, and you have...

At the moment I am about to enter my final year of an MSci Physics with Particle Physics and Cosmolgy. My final year project will have me working on particle detector R&D (looking at designs and radiation hard technologies to upgrade LHCb's ECAL). The natural progression from that was to do a...

Homework Statement hey I am trying to work out the problem: If I shoot an ak47 underwater with 7.62x39mm ammunition, how far will the bullet travel before coming to a stop? Homework Equations The equation that I have used to find the drag force is the drag equation: F =1/2 p*A*C_d*v^2...

In the classic time travel Sci-Fi film Back to the Future, Doc Brown presents us with a magnificent time machine in the sleek design of a Delorean . But what if the Doc hadn't chosen such a car. What would have Marty been in throughout the trilogy? What alternate time machines are there?

I am a trucker. I pull 53' dry van trailers with a big rig truck (a tractor). When a tractor-trailer backs straight backwards (not turning ) it is called straight line backing. Probably most people here know from backing boat trailers or other trailers at some point in their lives that when...

I've read somewhere that supersonic waves behave like supercritical flow of fluids and that subsonic waves behave similarly to that of subcritical flow. I guess an example of subcritical flow is pinching a hose and supercritical is how water flows over rocks (a bit more confused on that). Can...

I'm at an internship and I saw a container labeled ultrasonic gel, which is used to prevent air from coming between a scanner and the human body. This is necessary because apparently ultrasound doesn't travel through air well. Why is this? (don't say because the density is low, because I will...

Homework Statement The identical twins Speedo and Goslo join a migration from the Earth to Planet X, 19.0 ly away in a reference frame in which both planets are at rest. The twins, of the same age, depart at the same moment on different spacecraft . Speedo's spacecraft travels steadily at...

Assume you are given the following unique chance. You get to meet three people of your choosing (literally anybody) from the past or present. When meeting this person, you get to have a one hour conversation with the person. Assume language is not a problem. You cannot alter the course of...

I have been working with the Godel solution to the Einstein field equations which is known to contain closed time-like curves. The metric I am using is the following: ds2 = dt2/(2ω2) + (exdzdt)/ω2 + (e2xdz2)/(4ω2) - dx2/(2ω2) - dy2/(2ω2) This is sign convention (+ - - -) Now from what I've...

Assume that you are being sent back in time. You can choose the exact time period, but it has to be more than 200 years ago. You cannot bring anything with you. How would you use your current knowledge in order to survive? Would you be able to get rich/famous/powerful? Note: you cannot learn...

Hi, this is my first post on here. Let's say I departure from Earth in a spaceship and reach a speed very close to c, as I go faster time would run slower and I would feel as if I was going faster and faster with no speed limit, even though I'm not going faster than c. Because my time is...

Hello, My friends and I have had about a 3 month dicussion going regarding time travel.We have to get this right. Its also something they have been debating on their podcast. The question or argument is. In the movie "Back to The Future" Marty goes back in time from 1985 to 1955.which after...