Can anyone verify the historical authenticity of this photo?

Yea, it's so obvious! The kids shadows goes one way, and the tree has no shadow at all!

Well, I was specifically referring to the obvious deletion of the nuclear blast in the distance. Probably done by a concerned family member who wanted to delete any reminder of the blast that caused little Timmy to grow up to become a grotesquely mis-shapen homunculus.

This pick proves the picture in question is photoshopped. Some of the dust is missing. Doubtful both shots from different angles are identical. Background different.

I think the little boy is Lou Holtz.

I would suggest sending a note to these people:

http://www.nationalatomictestingmuseum.org

They are the La Vegas atomic testing museum and all days tours are run out of there to the former atom testing site.

If anyone would know about that picture they would and they are a very freindly group of people.

Given the amount of time for the mushroom to get to that stage, a few seconds, the photographer would be blind from the initial flash, and I would expect all their clothes to be on fire.

Seriously? Uh no. Shockwave is still otw, they have just a few seconds left to live.

Not really necessary to revive question threads that were clearly answered.
http://able2know.org/topic/248557-1#post-5706052

There's a famous photo of civilians observing the Operation Greenhouse "Dog" atomic blast in 1951, seated in Adirondack chairs and protected (cough) by dark goggles. This one is definitely not fake.

https://en.wikipedia.org/wiki/Operation_Greenhouse

There's a huge difference between military observers (established fact) and civilian observers (not referring to nonmilitary-related contractors, politicians, and scientists).

Children and family members? I doubt the government clearly didn't give them security clearance to witness such top secret military events.

There was an effort in the early 1950's to try to reverse the trend of having the public be afraid of the effects of nuclear weapons. The reason is clear and well documented: Military strategists wanted to ensure that there would be few if any restrictions on their use, even on American soil. They came up with scenarios such as an enemy attack in the American West with tanks rolling through California, which they'd like to repel with a tactical/battlefield nuclear weapon. Thus it was in their interest to show that civilians could live and thrive just a few miles from the blast zone. They did indeed bring in large numbers of civilian observers, including the press, as well as a full compliment of military staff. No, there weren't children freely roaming as in the fake photo at the start of this question, but not only were the non-military VIP observers in the Adirondack chairs real, there were also military observers placed even closer including directly under some of the bombs, in order to "prove" the survivability. Contrary to your assertion, these weren't "top secret military events" at this point, there was a massive public relations campaign going on, and an estimated 200,000 observers, both military and civilian, were brought in to see the show. This estimate comes from the U.S. Government National Institutes of Health:
http://www.ncbi.nlm.nih.gov/books/NBK225000/
Military observers directly underneath an exploding nuke were documented in this video, you can read more about it in the National Public Radio story at this link:
http://www.npr.org/sections/krulwich/2012/07/16/156851175/five-men-agree-to-stand-directly-under-an-exploding-nuclear-bomb

The larger military program of showing how "survivable" nuclear explosion regions are is covered in this government film:

I found some more legitimate photos of casual observers of nuclear mushroom clouds. The entire city of Las Vegas, Nevada was close enough to the above-ground Nevada nuclear bomb tests to observe the clouds, such as this one in 1957:

U.S. Government Dept. of Energy source:
http://www.nv.doe.gov/library/photos/photodetails.aspx?ID=787
According to Time Magazine:

http://time.com/3676511/nevada-nuclear-test/
The popularity of "atomic tourism" is described here by the Public Broadcasting Service (PBS)
http://www.pbs.org/wgbh/amex/lasvegas/peopleevents/e_atomictourism.html
An actual photograph including a child observing an atomic mushroom cloud in Las Vegas:

and a family observing the "nuclear dawn"

Photo credit: Alan Jarlson (1932-2007), Las Vegas Sun

Similar controversy regarding an atomic blast and a photoshopped photograph:
Nuked Bike Ride

Maybe Quantum mechanics can explain how Einstein's shadow turned into a shadow of Schrödinger's cat.

That would be a Joshua tree, from the Yucca bush family, which is a protected plant in Joshua Tree National Park. They are everywhere in the Mojave Desert (I used to live there) and can be found in the Colorado Desert. These trees can be located in CA, AZ, UT, and NV. More information can be found at: https://en.wikipedia.org/wiki/Yucca_brevifolia#Distribution_and_habitat

Thank you

Not a problem