The Lockheed SR-71 "Blackbird" is a long-range, high-altitude, Mach 3+ strategic reconnaissance aircraft developed and manufactured by the American aerospace company Lockheed Corporation. It was operated by both the United States Air Force (USAF) and NASA.The SR-71 was developed as a black project from the Lockheed A-12 reconnaissance aircraft during the 1960s by Lockheed's Skunk Works division. American aerospace engineer Clarence "Kelly" Johnson was responsible for many of the aircraft's innovative concepts. The shape of the SR-71 was based on that of the A-12, which was one of the first aircraft to be designed with a reduced radar cross-section. At one point, a bomber variant of the aircraft was under consideration, before the program was focused solely on reconnaissance. Mission equipment for the reconnaissance role included signals intelligence sensors, a side-looking airborne radar, and a photo camera; the SR-71 was both longer and heavier than the A-12, allowing it to hold more fuel as well as a two-seat cockpit. The SR-71 designation has been attributed to lobbying efforts by USAF Chief of Staff General Curtis LeMay, who preferred the SR (Strategic Reconnaissance) designation over simply RS (Reconnaissance, Strategic). The aircraft was introduced to operational service in January 1966.
During aerial reconnaissance missions, the SR-71 operated at high speeds and altitudes (Mach 3.2 and 85,000 feet, 25,900 meters) to allow it to outrace threats. If a surface-to-air missile launch was detected, the standard evasive action was simply to accelerate and outfly the missile. On average, each SR-71 could fly once per week due to the extended turnaround required after mission recovery. A total of 32 aircraft were built; 12 were lost in accidents with none lost to enemy action. During 1988, the USAF retired the SR-71 largely for political reasons; several were briefly reactivated during the 1990s before their second retirement in 1998. NASA was the final operator of the type, retiring their examples in 1999. Since its retirement, the SR-71's role has been taken up by a combination of reconnaissance satellites and unmanned aerial vehicles (UAVs); a proposed UAV successor, the SR-72 is under development by Lockheed Martin, and scheduled to fly in 2025. The SR-71 has been given several nicknames, including "Blackbird" and "Habu". As of 2020 the SR-71 continues to hold the official world record it set in 1976 for the fastest air-breathing manned aircraft, previously held by the related Lockheed YF-12.
We only measure time via the relative movement of a standard, agreed reference, a clock for example.
If we replaced all instances of "time" in the formulation of SR and GR by "relative motion [ie, of an agreed reference]", would SR/GR remain correct/consistent? Or does SR/GR rely on a deeper...
The Experimental basis of SR FAQ (https://www.physicsforums.com/threads/faq-experimental-basis-of-special-relativity.229034/) no longer seems to be stickied at the top of this forum. Perhaps five stickies would be too many, in which case I think it's worth adding to the FAQ list...
I guess it is safe to say that SR is, mathematically speaking, a framework that correlates discrete events in spacetime by way of a universal constant (the speed of light) so that the "proper distances" that separate them may be determined. I think this means that every conceivable "instant...
TL;DR Summary: How much special relativity Is needed for Edward M. Purcell & David J. Morin
It clearly is needed to fully understand this book and I have what seems like a good book that introduces relativity (A.P. French)
But I am not wanting to start it yet and it’s around 300 pages long...
This is a historical question regarding SR. Has any physicist before EInstein multiplied the time coordinate with the speed of light? If yes who was it? What is a good book or paper that discusses why and how Einstein (or others before him) have come up with the idea to multiply c and t?
When...
I am reshaping my course on special relativity (master level intermediate relativity course, I am getting it back after having the GR course instead for a number of years) and I find myself wanting to include two things:
- A more geometrical approach to Minkowski space.
- Basic classical...
SR interpreted as having no absolute frame of reference and an absolute frame type version of SR, where the speed of light is isotropic only in one undetectable frame are considered equivalent, since they use the same math.
But here is a scenario in which I don't see how the physical predictions...
I am taking a summer course on special relativity and I stumbled across this problem and solution which I tought look neat. However, I think the solution provided for a) there is wrong. I will here present two of my solutions for a) and one solution for b) and ask if you think mine are okay? :)...
Developers of Shape Dynamics (as Julian Barbour and Tim Koslowski) claim that Shape Dynamics will offer in most cases the same predictions as GR, and implicitly as SR. How can this possibly be true, since they get rid of time altogether and thus of any notion of simultaneity?
How would they get...
Is it possible to derive special relativity from the principle of quantum mechanics according to which particles of the same type are indistinguishable?
For example, if it is not possible to distinguish particles of the same type then particles colliding in a train at constant speed should...
[Moderator's note: Thread spun off from previous one due to topic shift.]
Please forgive my ignorance, I've never studied group theory systematically up to now, so I'm not aware of all the concepts and symbols that have been used up to now. Yet, I'm interested in the derivation of the Lorentz...
This thread, some earlier ones, and my signature got me thinking a bit about whether it would be a good idea to de-emphasize simultaneity when teaching SR since it is a frame dependent concept. I did not do much thinking myself yet but would like to hear people’s opinions and thoughts on how...
The thread:
https://www.physicsforums.com/threads/question-about-a-stronger-relativity-paradox-than-the-twin-paradox.1009978/
proposed an interesting SR scenario. The thread could have led to instructive discussion of exactly how relativity of simultaneity resolved a "false paradox" that...
Adopt the speed of light equals one.
Calls ##cos = c##, ##sin = s##
$$ux' = \frac{v-uc}{1-uvc}$$
$$uy' = \frac{us}{\gamma(1-uvc)}$$
$$tan \theta' = uy' / ux' = \frac{us}{\gamma(v-uc)}$$
So that's basically my solution. The problem is: The answer is ##\frac{us}{\gamma(v+uc)}##. Now, i can't...
There are some question involving the statement. One of them is about the charge density in S' frame. It asks to calc it.
I thought that i could calculate the electric field in the referencial frame S' and, then, use the formula
$$ E = \lambda / 2 \pi \epsilon l $$
In that way, i would obtain...
When I think of the speed of light being constant for all reference frames, I imagined the scenario in the picture below to exemplify it. Object A is always at rest, object B is moving at half the speed of light along the only given axis, and object C is a light particle moving at the speed of...
According to this link here https://en.wikipedia.org/wiki/Relativistic_mechanics#Force , we can inverse the relation of force in terms of velocity and acceleration:
$$
\mathbf{F} = \frac{m\gamma^3}{c^2}(\mathbf{v} \cdot \mathbf{a})\mathbf{v} + m\gamma\mathbf{a}
$$
to get:
$$
\mathbf{a} =...
I recently came across a book called advanced theoretical physics -nick lucid. chap6 covers tensors and chap 7&8 cover SR&GR. I have studied a bit of SR before but never GR. At this point in life I don't want to read huge books on the subject. this book covers relativity entirely in three...
Being mistaken gives me the creeps because, to the extent that truth matters, it's my only tool, shield, and weapon. So I'm always looking over my shoulder, worrying that I might believe something that's not true.
Are any of these NOT true?
The spacetime interval is "absolute distance,"...
Solutions are given in the book, but I could not understand some part of them.
For problem 2.2, denote the 4-momentum of the photon by ##\mathbf P_\gamma##, that of the particle by ##\mathbf P## and the values after scattering by primes.
Then by the conservation of momentum, we have ##...
One of my first exposures to special relativity was looking at a 'light clock' where a photon is emitted and captured by a detector whilst traveling on a train. The passenger sees the photon go straight up.
The distance traveled by this photon in a given time, t, is c t
An observer however...
Summary:: I have tried for some time to understand my error but can't figure it out. Any help will be much appreciated.
Hi!
I'm trying to figure out why the spatial displacement from two events A and B gives zero when I use one method compared to another which doesn't give zero spatial...
Hi,
I'm a 15-year-old high school student and I was wondering what textbook you guys recommend for Special- and General Relativity. I'm familiar with the concept of the Metric Tensor and Christoffel Symbols, but I wanted a good textbook where I can really learn derive it all and gain a deeper...
The 2 Bowling Balls
Ball(a) & Ball(b)
(a) is in acceleration of 10m/s^2
(b) is in at fixed position in a gravitational field where g=10m/s^2
In both cases the observer is:
- perpendicular to the vector of acceleration
- distant enough to be in empty flat space
Question : In an instantaneous...
Why aren’t all the SR effects cumulative like Time Dilation? Why should the Space dimensional effect become null when v—>0 while the Time dimension does not revert back to the 2 frames being in sync if Space and Time are treated on an equal footing. Clearly, Space and Time are not treated on an...
I was recommended a paper:
<https://digital.library.adelaide.edu.au/dspace/bitstream/2440/101285/3/hdl_101285.pdf>.
And in the opening sentence read: "The Einstein equivalence principle (EEP) is at the heart of special relativity."
To me this didn't make sense. Firstly because Einstein...
Sorry if this is discussed here previously, but I just stumbled upon an article from 1911 which I would like to bring forth to you.
Preamble: it is generally thought that Einstein's (refined) two axioms of SR (1. The laws of physics are invariant upon shifting from one IRF to another. 2. The...
I don't know much about the math of SR, but this is what's bothering me: if a moving clock B ticks slower than the stationary one I have (A), then from the viewpoint of B, my clock (A) is ticking slower. So if we turn around and meet each other in the middle, which clock was slower than which...
Hi. I am looking for some references of acceleration frame in SR, such as an accelerating rocket problem.
I have some equations regarding the time, distance, velocity measured in the Earth frame, etc. But the reference I have does not provide the derivation of those equations, so I need some...
At the very bottom of this page -
https://en.wikipedia.org/wiki/Minkowski_diagram
is the below animation. My understanding is that events in the lower triangle are events that can have had an influence on my present, they are in my past-lightcone. I understand that events must move in and...
I had this notion that it would be very easy to learn and understand Special Relativity, especially Time dilation.
Well, I was wrong.
First it will take the general history and philosophy of what Time Dilation is and how it works.
Then it takes Mathematical calculations.
In the end it takes a...
The problem I am having is "What can you conclude about wave prorogation in SR given the results?". The best I can come up with is that the number of wave planes N crossing a section of spacetime in either frame is the same. The section may be bigger or smaller depending on which frame you're in...
Well, using (1) is easy to see that, at a given time in C ##t## both curves are described with the same value of ##\tau##, i.e. ##\tau_A=\tau_B=\tau##. So the corresponding positions at a given time ##t## are
$$x_{AB}=x_{0,AB}+\frac{\cosh{(a\tau)}-1}{a}$$
and therefore
$$\Delta x \equiv x_B -...
Why shouldn't i be skeptical about SR postulate no.1 ??
From wiki (https://en.wikipedia.org/wiki/Special_relativity):
"1. the laws of physics are invariant (i.e. identical) in all inertial frames of reference (i.e. non-accelerating frames of reference) "
1. Particles aren't an experiment...
Hi all, I have ran into some confusion about the equivalence principle; perhaps I should state what I understand and then proceed to ask questions.
It is my understanding that the equivalence principle states that spacetimes are locally Minkowski, and so the rules of SR apply in that locality...
So, here's an attempted solution:
With ##r_{min}##,
$$r_{min} = \frac{1}{B + \frac{\beta}{\alpha^2}}$$
With ##r_{max}##,
I get:
$$r_{max} = \frac{1}{B - \frac{\beta}{\alpha^2}}$$
or
$$r_{max} = \frac{1}{\frac{\beta}{\alpha^2}}$$
Other than this, I and the team have absolutely no idea on how...
Below, I have already solved - I assume - correctly for question 1. Question 2, I am nearing to what I believe is the solution. Question 3, I simply have no idea where I should begin considering that it is interconnected with question 2.
With that said, below is the lengthy and somewhat tedious...
In Special Relativity I'm given the energy-momentum tensor for a perfect fluid:$$
T^{\mu\nu}=\left(\rho+p\right)U^\mu U^\nu+p\eta^{\mu\nu}
$$where ##\rho## is the energy density, ##p## is the pressure, ##U^\mu=\partial x^\mu/\partial\tau## is the four-velocity of the fluid. In the...
To begin with, I posted this thread ahead of time simply because I thought it may provide me some insight on how to solve for another problem that I have previously posted here: https://www.physicsforums.com/threads/special-relativity-test-particle-inside-suns-gravitational-field.983171/unread...
Suppose the time interval in the Lab frame is a multiple of the time interval in the Rocket frame ##\alpha \Delta t_L = \Delta t_R##, where ##0 < \alpha < 1## without loss of generality. Then the spacetime interval is
##\left( \Delta t_L\right) ^2-\left( \Delta x_L\right) ^2 = \left( \Delta...
Homework Statement: Problem:
The planet X is far 48 light-years from Earth. Suppose that we want to travel from Earth to planet X in a time no more than 23 years, as reckoned by clocks aboard our spaceship. At what constant speed would we have to travel? How long would the trip take as reckoned...
This question will sound mostly stupid but anyways.
We see that galaxies have some velocity due to the Hubble law. Let's take an object that has a recessional velocity of ##v##. In SR case assuming the universe is nearly flat, can we say that the galaxy gains mass relative to us ?
I guess in...
Hi all,
Consider the situation depicted in the illustration. Two identical 'square plates' are situated at rest, in frame S, as shown: Plate A has its thickness 'a' parallel to the x-axis and its sides 'L' parallel to the y and z axes, while plate B has its thickness parallel to the y-axis and...
It is often claimed in these forums and beyond that collapse in QM is completely unnecessary for one of several reasons. To be explicitly clear, collapse seen purely as a probability theoretical concept of conditional updating - i.e. treating the wavefunction as an epistemic object - isn't...
NASA has proposed a mission to Alpha Centuri:
https://en.wikipedia.org/wiki/2069_Alpha_Centauri_mission
This mission would involve a spacecraft traveling at 10% of light speed and therefore relativistic effects could be somewhat significant.
Let's assume this spacecraft is carrying a...
Homework Statement
Two particles in a high-energy accelerator experiment approach each other head-on with a relative speed of 0.890c. Both particles travel at the same speed as measured in the laboratory. What is the speed of each particle, as measured in the laboratory?
Homework Equations...
Suppose an observer (O) sees a traveler (T1) pass by at time t=0, moving a speed 3c/5. Five years later (according to O), T1 returns. If we assume that T1 traveled at 3c/5 for half the journey and instantaneously reversed direction, returning at the same speed, we can calculate that T1 aged only...