When the moon is in the seventh house, maybe you'll find the right astrological love match, but there are signs of the zodiac that no matter how the planets align, it just isn't in the stars.

Just like the elements they represent, fire (Aries, Sagittarius, Leo) and water (Cancer, Scorpio and Pisces) signs many times don't mix, and clashes of titans from the air (Gemini, Libra, Aquarius) and earth (Taurus, Virgo, Capricorn) signs have been known to move heaven and earth, and not in a good way.

But remember, this isn't an exact science. Sometimes fire and fire burn out too quickly (just ask Britney Spears and Kevin Federline) or earth plus water in the end just turns into ... well, mud (see Jim Carrey (Capricorn) and Jenny McCarthy (Scorpio) or perhaps even the royal couple of Prince William, a Cancer, and Kate Middleton, a Capricorn).

So before you jump feet first into an astrological love match nightmare, here are five of the absolute worst astrological pairings on the planet.

No. 5: Gemini and Aries

Gemini is the sign of the twin, so take that into consideration first and foremost. Known for their split personalities, they need a submissive companion sign to handle their on again, off again moods.

That submissiveness isn't something they are likely to find in large amounts should they find themselves falling for Aries.

Rather, when the chameleon-like Gemini has changed his/her personality one too many times, you can bet your lucky ram's horn keychain that the surefooted Aries is going to fly.

Gemini also has a deficit in the "seeing what's right in front of them" department, while Aries is prone to infidelity (Mr. Jesse James, I presume?).

This love match, in most cases, will be more volatile than a pinball machine. Tilt.

Famous Gemini-Aries couples -- past and present: Sandra Bullock (Gemini) and Jesse James (Aries), and Warren Beatty (Aries) and Annette Bening (Gemini).

No. 4: Cancer and Aquarius

Out and about Aquarius and couch potato Cancer will clash on many levels, but none more than intimacy and settling down.

The Aquarian's cool, almost iciness, demeanor will frustrate the emotional touchy feely Cancer, and it is difficult for the two to connect as Aquarius is guarded while Cancer pleads for openness. Aquarius likes their freedom, while clingy Cancer prefers to remain isolated in its hard crab shell.

While Aquarians are sexual adventure seekers, conservative Cancers lean more to the cuddly, sensual side of the bed. Family, home and stability are the three things that Cancers seek, while aloof Aquarius just lives to be the life of the party.

No one is saying the Crab and the Waterbearer can't find common ground, but let's just say that it's going to take a lotta love to change the way things are.

Famous Cancer-Aquarius couples -- past and present: Natalie Wood (Cancer) and Robert Wagner (Aquarius), Nancy (Cancer) and Ronald Reagan (Aquarius), and Lindsay Lohan and Wilmar Valderrama.

No. 3: Scorpio and Leo

Imagine a lion and a scorpion fighting to the death and this is exactly how the chemistry between a Leo and Scorpio would be.

Leo the lion is controlling as is the possessive Scorpio, and if you expect that sparks will fly in the bedroom, it will probably be more like pairs of shoes hurled at each other because of an explosive argument.

One astrologist said that many of these love matches end up in crimes of passion as Leo's tendency to keep secrets, especially about sexual attractions, won't fare well with the Scorpion's sting. Scorpios will also grow tired of Leo's constant need for ego stroking.

Famous Scorpio-Leo couples, past and present: Hillary (Scorpio) and Bill (Leo) Clinton, Maria Shriver (Scorpio) and Arnold Schwarzenegger (Leo), and Diana Krall (Scorpio) and Elvis Costello (Leo).

No. 2: Virgo and Sagittarius

The free-spirited Archer's arrow will pierce the stable heart of the Virgo, but watch as Virgo turns the arrow on Sadge to burst his dream bubble.

These two signs will find themselves frequently at a crossroads, a stand off, and even arguing about the color of the sky. While Sadge will point out dreamy flecks of pink during a sensual sunset, Virgo will remain down to earth and discuss dominant blue.