History often leaves unresolved mysteries that were later overshadowed by other, greater events. This eventually caused the mysteries to remain. Over the course of time, some researcher or a group will pick up a mystery and delve deeper, leading to highly interesting observations and rational explanations. Here are 10 strange mysteries from history that were solved in recent times:

1 On May 6, 1937, LZ 129 Hindenburg, a German passenger airship, caught fire during an attempt to dock, killing 35 people on board. Nothing conclusive came out from investigations, leaving room for conspiracy theories. Seventy-six years later, a team of researchers set fire to scale models of the Hindenburg and concluded that hydrogen leaking from a valve was set afire by the static charge from a thunderstorm.

In 2013, a team of researchers at the South West Research Institute, US, set fire to a series of 80-foot-long scale models of the German airship LZ 129 Hindenburg. It was an attempt to solve a 76-year-old mystery of the Hindenburg explosion.

On May 6, 1937, the 800-foot-long LZ 129 Hindenburg had exploded in flames when docking at the Naval Air Station Lakehurst after flying through a thunderstorm. Although many photographers and four cameramen captured the landing, no footage exists of the moment the fire started.

While eyewitnesses provided details such as the fluttering of the fabric (indicating a gas leak) ahead of the upper fin and flames of the shape of mushroom in front of the upper fin, these reports didn’t help investigators reach a definite conclusion and much was left to speculation and conspiracy theories. Then, 76 years later, aeronautical engineer Jem Stansfield and his team of researchers set upon the task of finding the reason behind the fire that killed 35 people out of the 97 onboard.

The team used a variety of methods to set fire to a series of scale models to determine the cause. The study concluded that the airship became charged with static electricity when maneuvering through the thunderstorm. Groundworkers holding the rope when docking created an earthing for the charge, initiating a spark. This ignited the leaking hydrogen. The fire, then, rapidly spread across the ship which then crashed tail-first to the ground. (1, 2)

2 In the Battle of Shiloh in 1862, some soldiers were found with wounds that emitted a faint blue glow. Medics found out that the soldiers with the blue wounds were more likely to survive, and thus they named it “Angel’s Glow.” Then in 2001, 17-year-old Civil War buff Bill Martin took interest in this case, along with his friend. They found out that Angel’s Glow was actually caused by a soil bacterium called Photorhabdus luminescens.

The Battle of Shiloh was fought on April 6 and 7, 1862. After the battle, many soldiers had to wait for up to two days for medics to reach and treat them in the field hospital. The medics observed that some soldiers who had a pale blue light emitting from their wounds were recovering much better and had a higher survival rate. They dubbed this live-saving glow “Angel’s Glow.”

Almost 140 years later, in 2001, Bill Martin and his friend visited the site and got involved in the case through the encouragement of Bill’s mother, who was a microbiologist. What was supposed to be an Angelic intervention was actually found out to be caused by a soil bacterium called Photorhabdus luminescens or P. luminescens, which live inside nematodes, parasitic worms that burrow into the blood vessels of larvae. Once they find an ideal host, the nematodes vomit up the bacteria, producing a chemical that kills the host, the surrounding microorganisms and pathogens, and creates the pale Angel’s Glow.

What is interesting is that these bacteria do not survive in normal human body temperatures, but since the soldiers were in rainy, muddy lands for extended periods of time, their body temperature had reduced drastically. (1, 2)

3 The Watergate Scandal was investigated and exposed by reporters Carl Bernstein and Bob Woodward. The crux of their information came from a secret informant called “Deep Throat,” whose identity remained unconfirmed for over 30 years. Suspects included George W. Bush, Mark Felt, and Nixon himself. It was only in 2005 that Mark Felt was confirmed himself to be the famed anonymous informant. 

In 1974, President Richard Nixon became the only president in American history to resign from office. A secret informant from the inside played a key role in divulging crucial information to Washington Post reporters Carl Bernstein and Bob Woodward for their book All the President’s Men.

The reporters had pursued the Watergate Scandal for two years before President Nixon’s resignation.

There were many candidates who were suspected to be the secret informant, dubbed “Deep Throat,” including Mark Felt, George W. Bush, and Richard Nixon himself.

The fact that Bob Woodward had great connections with Mark Felt and close connections saying Felt was indeed the informant grew speculations, but every speculation was denied by Felt, Woodward, and Bernstein.

It was only three decades later in 2005, when Mark Felt was 91 that he and Bob Woodward confirmed that Felt indeed was Deep Throat., thus concluding one of the most famous mysteries in American history. (1, 2, 3)

4 From 1948 to 1958, giant three-toed footprints of a mysterious creature were found on beaches of Florida. A few people, along with an investigating zoologist, claimed to have seen the 12-foot-long creature that was speculated to be a giant penguin. Forty years later, Tom Siginorini revealed that he, along with his boss had planted the footprints with iron feet as a prank.

In February 1948, beachgoers in the sleepy village of Clearwater, Florida found bizarre footprints in the sand. The three-toed prints were 14 inches long, 11 inches wide, and four to six feet apart. The gigantic creature appeared to have emerged from the water and walked for two miles before returning to the waves.

From Honeymoon Island to St. Pete Beach, all the beaches were stamped with mysterious tracks.

The news was received by the public with either skepticism or panic. NBC and the New York Herald-Tribune assigned Ivan Sanderson, a zoologist in pursuit of stardom, to investigate the matter.

Sanderson concluded that the prints were too deep to have been pressed by a machine or a man. He thought the footprints to be of a giant penguin. A few people, along with Sanderson, even claimed to have seen the 12-foot-long creature with large arms.

Over the next ten years, the tracks appeared a few more times.

Finally, in 1988, the mystery was solved when a Times reporter found himself at Tom Signorini’s automotive repair shop. There, Signorini showed the reported a pair of iron feet with three toes.

He revealed that the whole thing was an elaborate prank. His boss, Steven Williams, first came up with the plan after coming across a photo of a fossilized dinosaur footprint.

The feet were cast from iron, matching the one in the photograph. The long stride of six to seven feet was achieved by Signorini jumping with one foot planted on the ground. People who reported seeing the creature were friends of Williams. (1, 2)

5 On February 17, 1864, the H.L. Hunley, a confederate submarine, mysteriously sank after blasting the Union warship Housatonic with its spar-mounted torpedo. After 150 years, the fate of the crew came to light when researchers at Duke University in Durham conducted experiments on scale models. They concluded that the crew was instantly killed from the blast waves of its own weapon.

H.L. Hunley was a Confederate submarine employed in the Civil war. A spar-mounted torpedo was attached to the cigar-shaped, self-propelled submarine.

On February 17, 1864, the H.L. Hunley attacked the Union warship USS Housatonic by thrusting the torpedo into the hull of the warship. An explosion caused by 135 lbs of black powder sank the Union ship within five minutes, killing five of its crewmember.

Shortly afterward, in a mysterious turn of events, the H.L. Hunley was also consumed by the water.

It was only in 1955 that the sunken submarine was discovered, and was brought up to the ground in the year 2000. The intact vessel with the skeletal remains of the crew found seated at their stations deepened the mystery. There was no sign of any attempt to escape, and two holes in the hull didn’t provide any answers.

Then researchers at Duke University in Durham in North Carolina conducted a series of experiments on a 6.5-foot-long scale model of the Hunley, using the Navy blast software.

The findings suggest that the crewmembers of the Hunley were exposed to blast waves, killing them instantly. The explosion from the torpedo sent blast waves through the vessel, damaging the soft tissues in the brain and the lungs.

As the vessel was submerged in water and vibrations travel at different speeds through water and air, a combination of the two speeds called “the hot chocolate effect” proved lethal for the people inside the H.L. Hunley. (1, 2)