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What is the biggest thing Einstein was wrong about?

The funny thing about Einstein’s biggest blunder is that even when he was wrong - he was probably right.For years, Einstein did not believe that the Universe was expanding or contracting. Like most other scientists at the time, he believed that the Universe was constant in size. Although we now know that the Universe is expanding, this information had not yet been discovered, so we can perhaps forgive Einstein and all of his contemporaries for their mistake. Unfortunately for Einstein, the notion of a static Universe contrasted with his own General Theory of Relativity, which was very successful in explaining many aspects of the Universe. According to GR, the mass of the objects embedded in space - distant galaxies, for example - ought to cause the Universe to collapse in on itself. Since this obviously hadn’t happened, Einstein inserted a “fudge factor” into his calculations called the Cosmological Constant. The Cosmological Constant was some sort of mysterious repulsive force that caused distant objects to resist being pulled together by gravity. It maintained the scale of the Universe.When it was discovered that the Universe is expanding, the need for a Cosmological Constant apparently evaporated. Scientists understood that the galaxies had not yet pulled themselves together because they were being carried apart by the momentum of their expansion. Scientists started to conjecture that the Universe might one day halt its expansion and collapse in on itself, but that was still a matter of debate. In any case, Einstein’s GR appeared to have been saved without the need for a Cosmological Constant.Then scientists made a very strange discovery; not only is the Universe expanding…it’s accelerating, and it has been for about 4 billion years.Einstein’s Cosmological Constant, long ago abandoned, came roaring back in the guise of “dark energy”. Scientists still aren’t sure what dark energy is, or why it exists, but the benefit of advanced observations has convinced them that it is a real thing. So even though Einstein believed himself wrong for suggesting that there is some kind of repulsive energy embedded in space itself - further evidence suggests that he was not. In other words, he was wrong about being wrong.

What are some things that mechanical engineers know and others don't?

Pringles DesignPringles are something different from other chips. Pringles are designed take the geometry of a hyperbolic paraboloid. This is the reason why bottom-most Pringle doesn't crack. This shape won’t allow the chips to fly off the manufacturing line. More over fits between your tongue and the roof of your mouth perfectly.2. Aeroplane WindowsEver observed small holes at the bottom of an aeroplane window?These holes are called breath holes and these holes allows pressure to be balanced out between the cabin and gap between panes and it also releases moisture from the gap between the inner and outer panes, allowing the window to remain mostly fog-free.3. Stones on railway tracksDue to heavy mass and high speed of the trains the rails and wooden tie vibrate and there is a possibility of dislocation from its position. So these stones known as ballast are place on the tracks to keep wooden tie in its position.4. Cylindrical TankersCubes and Cuboids can carry more volume in the given space when compared to cylindrical or spherical shapes but still fluid carrying vehicles have cylindrical tank. The main reason is to avoid edges because stress concentration at the edges is much higher than the stress concentration at the bends. So the chances of failure of cylindrical tanks are much less compared to other.5. Tennis BallEven wondered why tennis balls are fuzzy?Tennis balls are made of bouncy rubber, the fuzz slows down the ball and keeps it from bouncing too high .7. Air Conditioner and Room HeaterAir conditioner are always placed on the top and room heater at ground level because they have got a reason to do so. Purpose of the AC is to cool the hot air and the density of hot air is less than density of cold air so it always raise pushing the cold air to ground level. this is the reason why AC are placed close to roof and heater are placed at ground level.8. World Trade Center CollapseTwin towers 417 m and 415 m tall collapsed in less that 10 seconds, but HOW?The main reason for quick collapse is phenomenon called CreepCreep: it is the tendency of a solid material to move slowly or deform permanently deformation under constant load over a long period of time.This creep increases with increase in temperature. During the collision the temperature reached up to 1000 degree Celsius, due to burning of jet fuel thus melting the steel beams and increasing the rate of creep.-The Dummy Batman